Methods and Apparatus for Signaling Sounding Reference Signals and Control Signals

ABSTRACT

A method implemented by an access node includes including transmitting, by the access node to a user equipment (UE), a control information message comprising an association indicator indicating an association between a reference signal and a channel between the access node and the UE; and communicating, by the access node with the UE, the reference signal in accordance with at least one channel parameter associated with the channel between the access node and the UE.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/US2021/040279, filed on Jul. 2, 2021, entitled “Methods andApparatus for Signaling Sounding Reference Signals and Control Signals,”which claims the benefit of U.S. Provisional Application No. 63/068,855,filed on Aug. 21, 2020, entitled “Methods and Apparatus for Sounding andControl Signaling Enhancements,” applications of which are herebyincorporated herein by reference in their entireties.

This application is related to Application No. PCT/US2021/040273, filedon Jul. 2, 2021, entitled “Methods and Apparatus for Configuration ofSounding Reference Signals,” application of which is incorporated byreference in entirety.

TECHNICAL FIELD

The present disclosure relates generally to methods and apparatus fordigital communications, and, in particular embodiments, to methods andapparatus for signaling sounding reference signals and control signals.

BACKGROUND

Sounding reference signals (SRSs) are reference signals transmitted byuser equipments (UEs) in the uplink for the purpose of enabling uplinkchannel estimation over a wide bandwidth. As such, the network may beable to perform communication with the UEs based on the uplink channelestimation. Moreover, due to channel reciprocity between the uplink andthe downlink present in a time division duplex (TDD) communicationsystem, the network may utilize the SRSs to perform dynamic scheduling.That is, the network may exploit channel-dependent scheduling. In thiscase, the time-frequency resources are dynamically scheduled, takinginto account the different traffic priorities and quality of servicesrequirements. Typically, the UEs monitor several Physical DownlinkControl Channels (PDCCHs) to acquire the scheduling decisions, which aresignaled to the UEs by the network. Upon the detection of a valid PDCCH,the UE follows the scheduling decision and receives (or transmits) data.

The configuration of SRS related parameters of a SRS to be transmittedin the uplink (such as SRS transmission ports, SRS transmissionbandwidth, SRS resources sets, transmission comb and cyclic shift, etc.)are semi-static in nature and may be provided through higher layersignaling, such as radio resource control (RRC) signaling. A moredynamic technique to signal the configuration is needed to betterassociate the SRS parameters (such as the SRS transmission bandwidthand/or ports) with the Physical Data Shared Channel (PDSCH) parameters.Moreover, the association between the downlink reference signals, suchas Channel State Information Reference Signals (CSI-RS) or demodulationreference signals (DMRS), and the uplink SRS must be conveyed to the UEto accurately reflect the interference situation and perform optimalbeamforming. Thus, there is a need for apparatus and methods forconfiguration of sounding reference signals, including signaling controlinformation that accurately indicates a more dynamic configuration (notsemi-static) of the aforementioned parameters, such as, for example, aportion of the transmission bandwidth required to transmit a subset ofthe SRS resource set (thereby implicitly indicating a transmission comband cyclic shift) using a subset of the transmission ports associatedwith a particular set of downlink reference signals. The signaling ofthe control information may be closely tied to an actual datatransmission. The transmission of the SRS may be periodic (i.e.,periodic SRS, P-SRS or P SRS) as configured by Layer 3 RRC configurationsignaling, semi-persistence (i.e., semi-persistent SRS, SP-SRS or SPSRS) activated/deactivated via Layer 2 media access control (MAC)control element (CE), or aperiodic (i.e., aperiodic SRS, A-SRS or AP-SRSor A SRS or AP SRS) indicated by Layer 1 downlink control information(DCI) in PDCCH.

SUMMARY

According to a first aspect, a method implemented by an access node isprovided. The method comprising: transmitting, by the access node to auser equipment (UE), a control information message, the controlinformation message comprising an association indicator indicating anassociation between a reference signal and a channel between the accessnode and the UE; and communicating, by the access node with the UE, thereference signal in accordance with at least one channel parameterassociated with the channel between the access node and the UE.

In a first implementation form of the method according to the firstaspect, the control information message comprising a downlink controlinformation (DCI) message.

In a second implementation form of the method according to the firstaspect or any preceding implementation form of the first aspect, thechannel being a physical downlink shared channel (PDSCH), and the atleast one channel parameter comprising at least one PDSCH parameter.

In a third implementation form of the method according to the firstaspect or any preceding implementation form of the first aspect, the atleast one PDSCH parameter comprising a frequency domain resourceassignment (FDRA) or an antenna port assignment.

In a fourth implementation form of the method according to the firstaspect or any preceding implementation form of the first aspect, theantenna port assignment comprising at least one of an antenna portnumber, an antenna port, and a number of layers.

In a fifth implementation form of the method according to the firstaspect or any preceding implementation form of the first aspect, theassociation indicator indicates an existence of the association betweenthe reference signal and the channel conveying a channel stateinformation (CSI) request.

In a sixth implementation form of the method according to the firstaspect or any preceding implementation form of the first aspect, the atleast one channel parameter comprising at least one CSI requestparameter.

In a seventh implementation form of the method according to the firstaspect or any preceding implementation form of the first aspect, thechannel being a PDSCH, and the PDSCH being scheduled by the DCI orconfigured as a semi-persistent scheduled (SPS) PDSCH.

In an eighth implementation form of the method according to the firstaspect or any preceding implementation form of the first aspect, thechannel being a physical uplink shared channel (PUSCH), the at least onechannel parameter comprising at least one PUSCH parameter.

In a ninth implementation form of the method according to the firstaspect or any preceding implementation form of the first aspect, theassociation indicator indicating a non-association between the referencesignal and the channel, and the method further comprising communicating,by the access node with the UE, the reference signal in accordance withparameters configured for the reference signal.

In a tenth implementation form of the method according to the firstaspect or any preceding implementation form of the first aspect,communicating the reference signal in accordance with the at least onechannel parameter comprising at least one of receiving, from the UE, thereference signal in accordance with at least one channel parameterassociated with the channel between the access node and the UE, ortransmitting, to the UE, the reference signal in accordance with atleast one channel parameter associated with the channel between theaccess node and the UE.

In an eleventh implementation form of the method according to the firstaspect or any preceding implementation form of the first aspect, the atleast one PUSCH parameter comprising at least one of a carrierindicator, an uplink (UL) indicator, a supplementary UL (SUL) indicator,a bandwidth part (BWP) indicator, a FDRA, a time domain resourceassignment (TDRA), a frequency hopping flag, a transmit power control(TPC) command, a SRS resource indicator, precoding information andnumber of layers information (TPMI), antenna ports, a SRS request, or aCSI request.

In a twelfth implementation form of the method according to the firstaspect or any preceding implementation form of the first aspect, thechannel being a PUSCH, and the control information message furthercomprising at least one of a SRS TDRA, or a SRS TPC command.

In a thirteenth implementation form of the method according to the firstaspect or any preceding implementation form of the first aspect, thereference signal comprising a sounding reference signal (SRS), a channelstate information reference signal (CSI-RS), or a CSI for interferencemeasurement (CSI-IM).

In a fourteenth implementation form of the method according to the firstaspect or any preceding implementation form of the first aspect, thechannel being a PUSCH, and the PUSCH being scheduled by the DCI orconfigured as a grant.

According to a second aspect, a method implemented by a UE is provided.The method comprising: receiving, by the UE from an access node, acontrol information message comprising an association indicatorindicating an association between a reference signal and a channelbetween the access node and the UE; and communicating, by the UE withthe access node, the reference signal in accordance with at least onechannel parameter associated with the channel between the access nodeand the UE.

In a first implementation form of the method according to the secondaspect, the control information message comprising a DCI message.

In a second implementation form of the method according to the secondaspect or any preceding implementation form of the second aspect, thechannel being a PDSCH, and the at least one channel parameter comprisingat least one PDSCH parameter.

In a third implementation form of the method according to the secondaspect or any preceding implementation form of the second aspect, the atleast one PDSCH parameter comprising a FDRA or an antenna portassignment.

In a fourth implementation form of the method according to the secondaspect or any preceding implementation form of the second aspect, theantenna port assignment comprising at least one of an antenna portnumber, an antenna port, and a number of layers.

In a fifth implementation form of the method according to the secondaspect or any preceding implementation form of the second aspect, thechannel being a PDSCH, and the PDSCH being scheduled by the DCI andconfigured as a SPS PDSCH.

In a sixth implementation form of the method according to the secondaspect or any preceding implementation form of the second aspect, thechannel being a PUSCH, the at least one channel parameter comprising atleast one PUSCH parameter.

In a seventh implementation form of the method according to the secondaspect or any preceding implementation form of the second aspect, theassociation indicator indicating a non-association between the referencesignal and the channel, and the method further comprising communicating,by the access node with the UE, the reference signal in accordance withparameters configured for the reference signal.

In an eighth implementation form of the method according to the secondaspect or any preceding implementation form of the second aspect,communicating the reference signal in accordance with the at least onechannel parameter comprising at least one of receiving, from the accessnode, the reference signal in accordance with at least one channelparameter associated with the channel between the access node and theUE, or transmitting, to the access node, the reference signal inaccordance with at least one channel parameter associated with thechannel between the access node and the UE.

In a ninth implementation form of the method according to the secondaspect or any preceding implementation form of the second aspect, the atleast one PUSCH parameter comprising at least one of a carrierindicator, an UL indicator, a SUL indicator, a BWP indicator, a TDRA, afrequency hopping flag, a TPC command, a SRS resource indicator, TPMI,antenna ports, a SRS request, or a CSI request.

In a tenth implementation form of the method according to the secondaspect or any preceding implementation form of the second aspect, thechannel being a PUSCH, and the control information message furthercomprising at least one of a SRS TDRA, or a SRS TPC command.

In an eleventh implementation form of the method according to the secondaspect or any preceding implementation form of the second aspect, thereference signal comprising a SRS, a CSI-RS, or a CSI-IM.

In a twelfth implementation form of the method according to the secondaspect or any preceding implementation form of the second aspect, thechannel being a PUSCH, and the PUSCH being scheduled by the DCI orconfigured as a grant.

According to a third aspect, an access node is provided. The access nodecomprising: one or more processors; and a non-transitory memory storagecomprising instructions that, when executed by the one or moreprocessors, cause the access node to: transmit, to a UE, a controlinformation message comprising an association indicator indicating anassociation between a reference signal and a channel between the accessnode and the UE; and communicate, with the UE, the reference signal inaccordance with at least one channel parameter associated with thechannel between the access node and the UE.

In a first implementation form of the access node according to the thirdaspect, the channel being a PDSCH, and the at least one channelparameter comprising at least one PDSCH parameter.

In a second implementation form of the access node according to thethird aspect or any preceding implementation form of the third aspect,the at least one PDSCH parameter comprising a FDRA or an antenna portassignment.

In a third implementation form of the access node according to the thirdaspect or any preceding implementation form of the third aspect, theantenna port assignment comprising at least one of an antenna portnumber, an antenna port, and a number of layers.

In a fourth implementation form of the access node according to thethird aspect or any preceding implementation form of the third aspect,the channel being a PDSCH, and the PDSCH being scheduled by the controlinformation message and configured as a SPS PDSCH.

In a fifth implementation form of the access node according to the thirdaspect or any preceding implementation form of the third aspect, thechannel being a PUSCH, the at least one channel parameter comprising atleast one PUSCH parameter.

In a sixth implementation form of the access node according to the thirdaspect or any preceding implementation form of the third aspect, theassociation indicator indicating a non-association between the referencesignal and the channel, and the programming causing the access node tocommunicate, with the UE, the reference signal in accordance withparameters configured for the reference signal.

In a seventh implementation form of the access node according to thethird aspect or any preceding implementation form of the third aspect,the programming causing the access node to receive, from the UE, thereference signal in accordance with at least one channel parameterassociated with the channel between the access node and the UE, ortransmit, to the UE, the reference signal in accordance with at leastone channel parameter associated with the channel between the accessnode and the UE.

In an eighth implementation form of the access node according to thethird aspect or any preceding implementation form of the third aspect,the at least one PUSCH parameter comprising at least one of a carrierindicator, an UL indicator, a SUL indicator, a BWP indicator, a FDRA, aTDRA, a frequency hopping flag, a TPC command, a SRS resource indicator,TPMI, antenna ports, a SRS request, or a CSI request.

In a ninth implementation form of the access node according to the thirdaspect or any preceding implementation form of the third aspect, thechannel being a PUSCH, and the control information message furthercomprising at least one of a SRS TDRA, or a SRS TPC command.

In a tenth implementation form of the access node according to the thirdaspect or any preceding implementation form of the third aspect, thereference signal comprising a SRS, a CSI-RS, or a CSI-IM.

In an eleventh implementation form of the access node according to thethird aspect or any preceding implementation form of the third aspect,the channel being a PUSCH, and the PUSCH being scheduled by the controlinformation message or configured as a grant.

An advantage of a preferred embodiment is that SRS configured parameters(SRS transmission bandwidth and/or ports) are associated with the PDSCHparameters (bandwidth and/or ports) and/or the CSI-RS parameters(bandwidth and/or ports).

Yet another advantage of a preferred embodiment is that controlinformation, such as the SRS transmission bandwidth, SRS transmissionports, and SRS resource sets including the SRS transmission comb andcyclic shift, are dynamically signaled for prescheduled (or scheduled)UEs after configuration through higher layer signaling, such as, forexample, through radio resource control (RRC) or media access control(MAC) control element (CE) signaling.

Yet another advantage of a preferred embodiment is that dynamicsignaling of the control information does not significantly increase thecommunications overhead, thereby minimizing the impact on the overallperformance of the communications system.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a first example communications system;

FIG. 2 illustrates an example communications system, providingmathematical expressions of signals transmitted in the communicationssystem;

FIG. 3 illustrates a flow diagram of operations occurring in aninterference probing process;

FIGS. 4 and 5 illustrate diagrams of RGBs, and example mapping of SRSresources and ports according to example embodiments presented herein;

FIG. 6 illustrates a diagram of messages exchanged by communicatingdevices performing interference probing according to example embodimentspresented herein;

FIG. 7 illustrates a first example DCI according to example embodimentspresented herein;

FIG. 8 illustrates a second example DCI according to example embodimentspresented herein;

FIG. 9 illustrates a third example DCI according to example embodimentspresented herein;

FIG. 10 illustrates a fourth example DCI according to exampleembodiments presented herein;

FIG. 11 illustrates a flow diagram of example operations occurring in aUE participating in interference probing and receives downlink dataaccording to example embodiments presented herein;

FIG. 12 illustrates a flow diagram of example operations occurring in anaccess node participating in interference probing and receives downlinkdata according to example embodiments presented herein;

FIG. 13 illustrates a flow diagram of example operations occurring in anaccess node configuring uplink SRSs according to example embodimentspresented herein;

FIG. 14 illustrates a flow diagram of example operations occurring in aUE transmitting uplink SRSs according to example embodiments presentedherein;

FIG. 15 illustrates an example one-shot BIT operation flow according toexample embodiments presented herein;

FIGS. 16A and 16B illustrate communication systems highlighting exampleinterference conditions according to example embodiments presentedherein;

FIG. 17 illustrates a diagram of information exchanged between an accessnode and a UE as the access node configures UL SRS sounding and thenmakes a DL transmission based on the UL SRS sounding results accordingto example embodiments presented herein;

FIG. 18 illustrates diagrams of RGBs with an example mapping of SRSresources and ports according to example embodiments presented herein;

FIG. 19A illustrates a flow diagram of example operations occurring in aUE communicating (e.g., transmitting or receiving) a reference signalbased on a reference signal association flag according to exampleembodiments presented herein;

FIG. 19B illustrates a flow diagram of example operations occurring inan access node receiving a reference signal based on a reference signalassociation flag for a reference signal trigger according to exampleembodiments presented herein;

FIG. 20A illustrates a flow diagram of example operations occurring in aUE communicating (e.g., transmitting or receiving) a reference signalbased on a reference signal association flag received in a DCI messagetriggering the reference signal transmission and scheduling a UL datatransmission according to example embodiments presented herein;

FIG. 20B illustrates a flow diagram of example operations occurring inan access node receiving a reference signal based on a reference signalassociation flag received in a DCI message according to exampleembodiments presented herein;

FIG. 21 illustrates an example communication system according to exampleembodiments presented herein;

FIGS. 22A and 22B illustrate example devices that may implement themethods and teachings according to this disclosure; and

FIG. 23 is a block diagram of a computing system that may be used forimplementing the devices and methods disclosed herein.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The structure and use of disclosed embodiments are discussed in detailbelow. It should be appreciated, however, that the present disclosureprovides many applicable concepts that can be embodied in a wide varietyof specific contexts. The specific embodiments discussed are merelyillustrative of specific structure and use of embodiments, and do notlimit the scope of the disclosure.

FIG. 1 illustrates a first example communications system boo.Communications system 100 includes an access node 110, with coveragearea 101, serving user equipments (UEs), such as UEs 120. Access node110 is connected to a backhaul network 115 that provides connectivity toservices and the Internet. In a first operating mode, communications toand from a UE passes through access node 110. In a second operatingmode, communications to and from a UE do not pass through access node110, however, access node 110 typically allocates resources used by theUE to communicate when specific conditions are met. Communicationbetween a UE pair in the second operating mode occurs over sidelinks125, comprising uni-directional communication links. Communicationbetween a UE and access node pair also occur over uni-directionalcommunication links, where the communication links between the UE andthe access node are referred to as uplinks 130, and the communicationlinks between the access node and UE is referred to as downlinks 135.

Access nodes may also be commonly referred to as Node Bs, evolved NodeBs (eNBs), next generation (NG) Node Bs (gNBs), master eNBs (MeNBs),secondary eNBs (SeNBs), master gNBs (MgNBs), secondary gNBs (SgNBs),network controllers, control nodes, base stations, access points,transmission points (TPs), transmission-reception points (TRPs), cells,carriers, macro cells, femtocells, pico cells, and so on, while UEs mayalso be commonly referred to as mobile stations, mobiles, terminals,users, subscribers, stations, and the like. It is noted that whenrelaying is used (based on relays, picos, CPEs, and so on), especiallymultihop relaying, the boundary between a controller and node controlledby the controller may become blurry, and a dual node (either thecontroller or the node controlled by the controller) deployment where afirst node that provides configuration or control information to asecond node is considered to be the controller. Likewise, the concept ofUL and DL transmissions can be extended as well.

A cell may include one or more bandwidth parts (BWPs) for UL or DLallocated for a UE. Each BWP may have its own BWP-specific numerologyand configuration. It is noted that not all BWPs need to be active atthe same time for the UE. A cell may correspond to one or more carriers.Typically, one cell (a primary cell (PCell) or a secondary cell (SCell),for example) is a component carrier (a primary component carrier (PCC)or a secondary CC (SCC), for example). For some cells, each cell mayinclude multiple carriers in UL, one carrier is referred to as an ULcarrier or non-supplementary UL (non-SUL) UL carrier which has anassociated DL, and other carriers are called a supplementary UL (SUL)carriers which do not have an associated DL. A cell, or a carrier, maybe configured with slot or subframe formats comprised of DL and ULsymbols, and that cell or carrier is seen as operating in time divisionduplexed (TDD) mode. In general, for unpaired spectrum, the cells orcarriers are in TDD mode, and for paired spectrum, the cells or carrierare in a frequency division duplexed (FDD) mode.

Access nodes may provide wireless access in accordance with one or morewireless communication protocols, e.g., the Third Generation PartnershipProject (3GPP) long term evolution (LTE), LTE advanced (LTE-A), 5G, 5GLTE, 5G NR, sixth generation (6G), High Speed Packet Access (HSPA), theIEEE 802.11 family of standards, such as 802.11a/b/g/n/ac/ad/ax/ay/be,etc. As used herein, the term network refers to entities of acommunications system other than UEs. While it is understood thatcommunications systems may employ multiple access nodes capable ofcommunicating with a number of UEs, only one access node and two UEs areillustrated for simplicity.

In standard antenna element to element channel estimation, a channelbetween two devices is estimated by having a first device transmit aknown signal on a known time or frequency resource(s) to a seconddevice, the received signal at the second device is expressible as:

y=Hx+n  (1)

where y is the received signal at the second device, x is the knownsignal (which may be a reference signal, a pilot, or a pilot signal), His the channel model or response, and n is the noise (and interferencefor some communication channels). Because x is known by the seconddevice, it is possible for the second device to determine or estimate Hfrom y.

It is noted that the concept of antenna, antenna element, and antennaport may be generally interchangeable, but in some specific scenarios,they can mean different but related subjects. For example, one transmit(Tx) antenna port may be formed (or virtualized) by multiple antennaelements or antennas, and the receiver sees only the one Tx antenna portbut not each of the multiple antenna elements or antennas. Thevirtualization may be achieved via beamforming, for example.

FIG. 2 illustrates an example communications system 200, providingmathematical expressions of signals transmitted in the communicationssystem. Communications system 200 includes an access node 205communicating with UE 210. As shown in FIG. 2 , access node 205 is usinga transmit filter v and UE 210 is using a receive filter w. Both accessnode 205 and UE 210 use linear precoding or combining. Assuming H isN_(rx)×N_(tx) matrix of a MIMO system, i.e., there are N_(tx) transmitantennas and N_(rx) receive antennas. The transmit filter v of dimensionN_(tx)×Ns enables the transmitter to precode or beamform the transmittedsignal, where Ns is the number of layers, streams, symbols, pilots,messages, or known sequences transmitted. The receive filter w ofmulti-antenna systems is of dimension N_(rx)×Ns and represents thecombining matrix. It is noted that the above description is for atransmission from access node 205 to UE 210, i.e., a downlinktransmission. The transmission may also occur at the reverse direction(an uplink transmission), for which the channel matrix becomes H^(H),which is the Hermitian of channel model H, and w may be seen as thetransmit filter and v as the receiver filter. The w for transmission andthe w for reception may or may not be the same, and likewise for v.

A downlink (or forward) channel 215 between access node 205 and UE 210has channel model or response H, while an uplink (or backward, orreverse) channel 220 between UE 210 and access node 205 has channelmodel or response H^(H), which is the Hermitian of channel model H.Although FIG. 2 depicts only one access node and one UE, it is notlimited to this case. Multiple UEs may be served by the access node, ondifferent time-frequency resources (such as FDM-TDM, as in typicalcellular systems) or on the same time-frequency resources (such asMU-MIMO, wherein multiple UEs are paired together and each UE isindividually precoded). Among the paired UEs, there is intra-cellinterference. Also multiple access nodes may exist in the network, someof which may be cooperatively serving UE 210 in a joint transmissionfashion (such as coherent joint transmission, non-coherent jointtransmission, coordinated multipoint transmission etc.), dynamic pointswitching fashion, and so on. Some other access nodes may not serve UE210 and their transmissions to their UEs cause inter-cell interferenceto UE 210. The scenario of multiple access nodes and multiple UEs, withaccess node cooperation to serve a UE and with MU-MIMO, is a scenarioconsidered herein, and the example embodiments of bi-directionaltraining applies to this scenario.

According to an example embodiment, precoded, unprecoded, or bothprecoded and unprecoded uplink SRSs are transmitted by UEs to accessnodes to assist in dynamic scheduling. These uplink SRSs includespecific transmission parameters (such as specific transmission ports,transmission comb, cyclic shift, transmission bandwidth (related to theSRS resources), etc.) that may be configured through higher layersignaling (such as through radio resource control (RRC) or media accesscontrol (MAC) control element (CE) signaling, for example). In somecases, the uplink SRS may be unprecoded to support uplink channelestimation and assist the network in prescheduling. Upon performinguplink channel estimation, the network preschedules UEs. Theprescheduling of UEs may involve a selection of UEs from a plurality ofUEs configured by the access node, where the selected UEs comprise UEsthat are suitable for receiving (or transmitting) data. Hence, theselected UEs comprise a subset of the plurality of UEs configured by theaccess node. The selected UEs may be referred to as prescheduled UEs.The suitability of a UE may be determined based on factors such aschannel quality, signal quality, error rate, data transfer history,quality of service restrictions, etc.

The prescheduling of UEs may precede an actual scheduling required for adata transmission (or reception) and the actual data transmission (orreception). In general, scheduling is not predictable. That is, thenumber of UEs and which subset of UEs selected for prescheduling are notknown during higher layer configuration. Therefore, after prescheduling,the network may decide to re-configure the semi-static configured SRSparameters based on the subset of UEs chosen in prescheduling. As such,apparatus and methods for configuration of SRSs are needed.

Interference probing and prescheduling may be performed by the networkafter UEs transmit the uplink SRS. As described previously,prescheduling is a process where the access node selects a subset of theUEs, which the access node has configured, for data transmission orreception. The selected UEs may be configured to transmit precoded SRSs.These precoded SRSs may be referred to as triggered SRSs. The accessnode may use the precoded SRSs to determine a downlink precoder(referred to as transmit filter v in FIG. 2 above). The preschedulingmay precede the actual scheduling for data transmission (or reception)and may be performed during a training phase (such as for example duringbi-directional training (BIT)) to determine the downlink precoder (andcombiners).

BIT, also commonly referred to as forward-backward training, is agenerally distributed training procedure with low computationalcomplexity that is used to train and update transmit precoders andreceive combiners without explicitly estimating the CSI. BIT may adapttransmit beamformers (which may also be commonly known as transmitprecoders, transmission filters, spatial transmission filters, transmitfilter, analog precoder, and the like) and receiver combiners (which arealso commonly known as receive filter, spatial receive filters, analogcombiner, and the like) in TDD MIMO communications systems. In BIT,neither device (a transmitting device or a receiving device)participating in BIT may have a priori knowledge of CSI, especiallydetailed information about the channel such as channel matrix H orcovariance matrix of the channel, wherein the channel may be one betweena UE and its serving access node(s) or one between the UE and itsinterfering access node(s) (which generally requires informationexchanges among access nodes, such as channel information about aninterfering link or RS information so that the UE or access node canestimate the interfering link).

An iterative form of BIT consists of forward training (e.g., in adownlink direction) and backward training (e.g., in an uplink direction)that is repeated until convergence is achieved. A one-shot form of BITcomprises a single forward training step and a single backward trainingstep. In general, BIT is capable of adapting to unknown interference andcan suppress interference without any channel estimation or CSIfeedback, thereby making BIT less sensitive to the orthogonality oftraining sequences. A more detailed discussion of BIT is presented inco-assigned patent application entitled “System and Method forCommunications System Training,” application Ser. No. 15/983,692, filedMay 18, 2018, which is hereby incorporated herein by reference in itsentirety.

Uplink probing involves the estimation of uplink channels between theaccess node and UEs served by the access node after reception of theuplink SRS, which reflects the interference situation at neighboringcells.

FIG. 3 illustrates a flow diagram of operations 300 occurring in aninterference probing process. Operations 300 may be indicative ofoperations occurring in an interference probing process involving anaccess node and one or more UEs.

Operations 300 begin with the one or more UEs transmitting uplink SRSs(block 305). The uplink SRSs may be transmitted by active UEs that areconfigured by the access node, and may be used for uplink channelestimation of the uplink channels between the configured UEs and theaccess node. In addition to being used for uplink channel estimation,the uplink SRSs may be used by the access node to select UEs forprescheduling. As discussed previously, prescheduled UEs are UEsselected by the access node, from of the access node's configured UEs,to transmit trigger based uplink SRSs, which are used by the access nodeto determine downlink precoders. In an embodiment, the uplink SRSstransmitted by the UEs in block 305 may be unprecoded. In an embodiment,instead of the uplink SRSs, feedback transmitted by the UEs is used bythe access node to select UEs for prescheduling. The access nodeperforms uplink channel estimation (block 307). The estimation of theuplink channels is performed using the uplink SRSs transmitted by theUEs, for example. As an example, the access node makes measurements ofthe uplink SRSs, and determines the estimates of the uplink channelsbased on the measurements of the uplink SRSs and the knowledge of theuplink SRSs. Alternatively, the estimation of the uplink channels isperformed using the feedback transmitted by the UEs.

The access node preschedules the UEs (block 309). The access node maypreschedule UEs based on the uplink SRSs or feedback received from theUEs. As an example, the access node selects the UEs associated with theuplink SRS (or feedback) received with highest signal quality measure.Examples of signal quality measures include signal to interference plusnoise ratio (SINR), signal to noise ratio (SNR), reference signalreceived power (RSRP), reference signal received quality (RSRQ),received signal power, and so on. The access node may select the UEsassociated with uplink SRSs received with signal quality measures thatexceed a specified threshold. The specified threshold may be specifiedin a technical standard, an operator of the communication system, orthrough collaboration between the access node and the UEs, for example.The access node may select a specified number of UEs associated withuplink reference signals received with signal quality measures thatexceed a specified threshold. The specified number may be specified in atechnical standard, an operator of the communication system, or throughcollaboration between the access node and the UEs, for example. As anexample, the access node may preschedule UEs based on the channelquality indicator (CQI) of the uplink channels, or the precoding matrixindicator (PMI) associated with the UEs.

The access node transmits downlink control information, e.g., in adownlink control information (DCI), intended for the prescheduled UEs totrigger SRS transmission with specific parameters and to assist UEs inthe measurement (e.g., use) of the downlink ports. The downlink controlinformation may provide to the prescheduled UEs the SRS parameters, aswell as related downlink associations. In other words, the downlinkcontrol information configures the SRS parameters and the relateddownlink associations. The downlink control information may indicate tothe prescheduled UEs which of the downlink channel state informationreference signal (CSI-RS) are assigned to the prescheduled UEs forproper measurement and determination of downlink combiner and/or uplinkprecoder. In an embodiment, the DCI may be group based DCI addressing agroup of UEs (e.g., all of active UEs or a subset of active UEs). Inanother embodiment, the DCI may be unicast DCI (such as 5G NR DCIs)addressed to a UE. The DCI (in either case) includes modified or addedfields that signal the SRS parameters.

The access node may transmit CSI-RSs (block 311). The CSI-RSs (if theaccess node is to transmit the CSI-RSs) may be transmitted in a precodedor unprecoded manner. The UEs may perform downlink channel estimation(block 313). In situations where the access node transmits the CSI-RSs,the UE performs downlink channel estimation in accordance with thereceived CSI-RSs. In an embodiment, only the UEs that received thedownlink control signals (i.e., the prescheduled UEs) perform downlinkchannel estimation.

The prescheduled UEs transmit triggered uplink SRSs (block 315). Theprescheduled UEs transmit the uplink SRSs as configured by the downlinkcontrol signals. In an embodiment, the uplink SRSs are precoded or areunprecoded (with no information contained therein). The uplink SRSs aretransmitted in accordance with the SRS configuration. As an example, aprescheduled UE transmits its uplink SRS in configured SRS resources,over configured transmission ports, using configured subbands, combs,and cyclic shifts, and with configured transmission bandwidth, asconfigured by the downlink control signals.

The configuration of the SRS parameters such as the SRS resource sets(SRS resources within a set), SRS transmission bandwidth, SRStransmission ports, SRS transmission comb and cyclic shift, etc., may beperformed using higher layer configuration. Arrangements of SRSresources or ports may be defined by the network and the network mayconfigure the UEs with the different arrangements. In addition, thenetwork may configure the UEs with a different mappings (e.g.,relationships, associations) between downlink ports, layers, referencesignals (such as demodulation reference signals (DMRS), CSI-RS), anduplink port or layers (SRS).

An important factor in supporting BIT and various SRS enhancements is toincrease the flexibility of A-SRS triggering, for at least the followingmotivations, in addition to the BIT related motivations. That is, theflexible A-SRS triggering may be designed and used beyond BITapplications.

Limited triggering information in existing DCIs (1, 2, or 3 bits only):SRS transmissions are associated with many parameters, such as comb,cyclic shift, transmission bandwidth in terms of the number of PRBs, onUL or SUL of a serving cell, antenna port(s), etc. In existingstandards, A-SRS can be triggered via a SRS request field in a DCI, andthe field may include 1, 2, or 3 bits. These bits can indicate 1)certain indicated SRS resource set(s) of the current serving cell, or 2)SRS resource set(s) on certain indicated serving cells, or 3) one of theUL and SUL. However, many other SRS transmission parameters cannot beindicated in DCI and can only be specified in RRC configurationsignaling. For example, because of the DCI bitwidth limitation, thenetwork may have to configure a few SRS resource sets together orconfigure a few serving cells together, i.e., these sets have to betriggered together, which is typically highly undesirable. In general,the limited triggering information leads to lack of flexibility in manyapplications as outline below, and hence it is a motivation to improvethe A-SRS triggering flexibility.

Lack flexibility in triggering offset (delay): In existing standards,the A-SRS triggering offset is configured via RRC field slotOffset andcan range from 1˜32 slots, and if this field is not configured, then 0slot offset is applied. This can be limiting in several cases. Forexample, when using the group-common (GC) DCI format 2_3 to trigger SRSfor a group of UEs on one or more of their serving cells, all the SRStransmissions are to occur after their pre-configured offsets withrespect to the same DCI triggering slot. This may impose significantrestriction on network's decision on which slot to send the GC DCI. Foranother example, SRS triggering by a DL DCI is likely to collide withthe acknowledgement or negative acknowledgement (A/N) associated withthe DL DCI, and SRS triggering by a UL DCI is likely to collide with thePUSCH associated with the UL DCI, especially in TDD communicationssystems when the UL slots occur less frequently. In general, the mainpurpose of A-SRS triggering is to provide flexibility in SRS timing, butthe pre-determined timeline in the triggering offset along with themostly fixed slot structure cannot serve that purpose well. Enhancementsare therefore needed.

Various vital roles of A-SRS: The A-SRS plays vital roles in TDD DL fullMIMO CSI acquisition, TDD or FDD UL CSI acquisition, frequency range 2(FR2) beam management, frequency-selective scheduling, UL timing advance(TA) maintenance, positioning, etc. As also considered in 3GPP workitems (WI), it is also crucial for FDD DL performance. However, the lackof flexibility described above regarding SRS triggering limits theusefulness of the SRS. For instance, if the SRS is dropped due tocollisions caused by inflexibility in triggering offset described above,then CSI acquisition and frequency-selective scheduling may benegatively impacted. CSI acquisition and frequency-selective schedulingcan be highly dynamic and therefore periodic or semi-periodic SRSs(P/SP-SRSs) are not suitable. In LTE Rel-14 SRS carrier-based switching,autonomous A-SRS retransmission is introduced so that a dropped A-SRStriggered by a DL DCI (i.e., after colliding with A/N) would beautonomously retransmitted in the next configured SRS transmissionoccasion, but this feature is not yet supported in 5G NR. To makeP/SP-SRSs and A-SRSs complement each other, P/SP-SRSs can be configuredwith long periodicities (to avoid excessive overhead and complexity) andthe network relies on the A-SRS for fast response to changes in trafficload and CSI (especially dynamic interference). Therefore, flexibleA-SRS triggering can be beneficial in many cases due to various vitalroles played by the A-SRS and should be supported.

Tightly related to SRS capacity or coverage enhancements: SRS coverageor capacity enhancements may include, but not limited to: 1) SRScapacity enhancement via SRS on partial bandwidth, for which thebandwidth may be dynamically indicated via DCI; 2) SRS capacityenhancement via SRS transmissions on unused PRBs or symbols in the PUSCHor PDSCH region, for which the SRS time-frequency resources may bedynamically indicated via DCI on the fly based on unused resources of aTTI; 3) SRS capacity enhancement via SRS multiplexed (on the samesymbol) with other signals, e.g., A/N, to accommodate flexible SRSmultiplexing to maximize SRS capacity; 4) SRS coverage enhancements vianarrow-band transmission based on frequency selectivity (rather thanpre-configured PRBs), and so on. Some of the enhancements are alsoapplicable to P/SP-SRS, however, especially for capacity enhancement,the SRS needs to have sufficient flexibility, e.g., when the networkidentifies a chance for A-SRS to opportunistically fill a gap intime-frequency resources (e.g., an unoccupied symbol in a slot, a fewunoccupied PRBs, etc.) it would trigger the UE to perform the A-SRStransmission. Therefore, flexible triggering of A-SRS can be also usefulto SRS capacity or coverage enhancements.

In order to effectively convey information about dynamic interferenceconditions to the network, an access node can indicate to UEs how theSRS should be transmitted, including the time or frequency resourceallocation and port selection for the SRS corresponding to theprospective PDSCH. This means that the network needs to dynamicallyadjust more SRS transmission parameters (PRB allocations, portselection, etc.) than with conventional SRS transmissions. Embodimentsare provided for SRS transmission with parameters tied to DLtransmission, including PRB allocation and port allocation.

In an embodiment, an indication of A-SRS PRB/port allocation isprovided. The SRS PRB/port allocation should be the same as theprospective PDSCH and should be dynamically indicated.

In an embodiment, an A-SRS beamforming indication is provided. The SRSbeamforming can be based on DL channel measurement resources (CMRs), andto better reflect potential DL interference, it is more desirable to bebased on DL CMRs and interference measurement resources (IMRs), one orboth of which may be dynamically indicated. In an embodiment, an A-SRStriggering offset is provided. In order to utilize the A-SRS to estimatethe interference for interference mitigation via precoding adjustment,the access nodes may not need to detect each UE's SRS sequences. Thereceived SRS power accumulated on each access node's receiving antennaport should be sufficient. Thus, the A-SRS can be transmitted onoverlapping resources to reduce overhead. However, the A-SRS triggersmay be sent to different UEs at different times. In order to enableA-SRS overlap, the A-SRS triggering offsets may be dynamically indicatedto different UEs. The A-SRS triggering offset may be similar to the kooffset and start and length indicator value (SLIV) design for PDSCH, forexample. In order to further reduce overhead, ko and SLIV may not referto the absolute slot or symbol offsets but slot or symbol offsets basedon configured SRS slots or symbols.

In an embodiment, a higher priority for A-SRS with newly introducedflexibility is provided. The A-SRS with newly introduced parameters in aSRS request field supports BIT and other enhancements may be assignedwith higher priority, so that when the A-SRS collides with other SRS orUL transmissions, the other transmissions (i.e., the transmissionscolliding with the A-SRS) are dropped.

In an embodiment, after the reception of the uplink SRS, access nodespreschedules UEs and indicates to the prescheduled UEs through thesignaling of parameters, including which portion of the SRS transmissionbandwidth, which SRS resources or ports from the different SRS resourcesor ports arrangements, transmission comb, cyclic shift, and which of thedownlink CSI-RS ports (and/or DMRS) are assigned to the prescheduledUEs. In addition to the listed parameters, the indication signaled tothe prescheduled UEs may include an association (e.g., mappings,relationships) between the uplink ports, the downlink ports, orbandwidth. The downlink ports may consist of the DMRS or CSI-RS ports.In an embodiment, the network uses a group DCI message to dynamicallyconfigure the SRS parameters. In another embodiment, a unicast DCImessage is used to dynamically configure the SRS parameters. The SRSstransmitted by the prescheduled UEs may be referred to as triggered SRSto differentiate them from the uplink SRSs that are transmitted by theUEs to facilitate uplink channel estimation, such as discussed in block305 of FIG. 3 . The uplink reference signals (e.g., the SRSs) are usedto convey interference situation in the neighboring cells, as well asthe serving access node's accounting of the interference suppressionreceiver capability of the UE. Subsequently, the access node determinesthe downlink precoder (in accordance with the received precoded SRSs(i.e., the triggered SRSs), for example) and transmits downlink datautilizing the downlink precoder.

The following discussion provides additional details on the indicationof the SRS transmission parameters.

As related to signaling the SRS Resources or Ports, the networkindicates to the UEs which of the SRS resources or ports are assigned tothe UEs. In other words, the UE needs to know which resource of the SRSresource pool or subset of the SRS configured resources to transmit onin the uplink transmission of the precoded SRSs.

In an embodiment, the network configures the UE with differentarrangements of resources or ports. The different arrangements of theresources or ports may differ by the cyclic shift, transmission comb,number of symbols (e.g., orthogonal frequency division multiplexed(OFDM) symbols), etc., for example. The different arrangements representdifferent mechanisms the network may pack the UEs SRS resources orports. In an embodiment, the different resources or ports arrangementsare predefined. Signaling a predefined arrangement of resources or portsmay require less overhead than signaling the different values for thecyclic shift, transmission comb, number of symbols (e.g., OFDM symbols),etc. As an example, if there are 8 predefined arrangements, signalingany one of the 8 may be accomplished by signaling a 3-bit index, whilesignaling the different values may require significantly more than 3bits. The predefined arrangements may be defined in the 3GPP standard orbe higher layer configured, the network may downsize (further select andsignal) a particular configuration after prescheduling (or scheduling)and may signal the downsized arrangement to the UE using DCI, forexample.

As an illustrative example of SRS resource or port signaling, consider acommunication system with 8 type 1 demodulation reference signal (DMRS)ports. In an embodiment, 12 DMRS ports may be used as an illustrativeexample, with a total of 8 uplink SRS resources (e.g., ports) for allUEs operating within a single cell and that 8 UEs are prescheduled.There is a need for the UEs to know which of the 8 uplink SRS resourcesto transmit on. Therefore, there is a need to signal, to the UEs toinform the UE which uplink SRS resource (or resources) to use, in anefficient way that minimizes impact on overall communication systemperformance. Informing the UEs which uplink SRS resources to use mayinvolve indicating which comb, symbol, cyclic shift, number of OFDMsymbols, etc., to use. As discussed previously, in one embodiment, theUEs may be configured with different arrangements of these SRS resourcesor ports. These arrangements may be specified in a technical standard,by an operator of the communication system, or determined throughcollaboration between communicating devices, for example. Examplearrangements include:

-   -   1 physical resource with 8 ports for 8 UEs having cyclic shift 8        (for orthogonality between ports) and comb 2;    -   1 physical resources with 8 ports for 8 UEs having cyclic shift        8 and comb 4;    -   8 physical resources with 1 port for each of the 8 UE;    -   2 physical resources with 4 ports per resources using cyclic        shift 4

In a first example embodiment, there is 1 physical resource with 8 portsfor the 8 UEs served within the cell, with a cyclic shift of 8 (ensuringorthogonality of SRS transmission), a comb of 2, and repetition over aspecified number of symbols (the specified number of symbols may bespecified in a technical standard, by an operator of the communicationsystem, or determined through collaboration between communicatingdevices, for example). In order to indicate to the UEs which one of the8 resource arrangements to use, a 3-bit indication is sufficient.

In a second example embodiment, there is 1 physical resource with 8ports for the 8 UEs operating within the cell, with a cyclic shift of 8,and a comb of 4. In order to indicate to the UEs which one of the 8resource arrangements to use, a 3-bit indication is sufficient.

In a third example embodiment, there are 8 physical resources with 1port per physical resource for each UE operating within the cell, withOFDM symbol multiplexing. In order to indicate to the UEs which one ofthe 8 resource arrangements to use, a 3-bit indication is sufficient.

In a fourth example embodiment, there are 2 physical resources with 4ports per physical resource for each UE operating within the cell, witha cyclic shift of 4. In order to indicate to the UEs which one of the 8resource arrangements to use, a 4-bit indication is sufficient if someUEs are allocated more than one port, e.g., a UE may be allocated 2ports.

These different resource or port arrangements may be predefined and thenetwork may configure the UE with the different arrangement. The networkmay signal one or more of these arrangements using DCI for the subset of(prescheduled, scheduled, active) UEs.

The examples presented above are only examples of resource configurationand the actual configuration may not be limited to the aforementionedresource configurations. In this case the network may use a certainnumber of bits (for example 3 to 4 bits) in the DCI to indicate to theUE which of the arrangements of resources or ports (implicitlyindicating the transmission layers, comb and cyclic shift) is assignedto the UE.

In an embodiment, the network may define a full set of SRS resources orports and use an indication to indicate a subset thereof. Such a designis similar to the DMRS port indication in 5G NR. In another embodiment,the network may define the subset of SRS resources or ports and use theindication to indicate the subset of the configured subsets. In any ofthese embodiments, a table may be used to summarize all the possibleresources set or subsets with the ports (ranks) which may be tied to thecyclic shift, comb, OFDM symbols, offset, etc.

The network may define a DCI bit indication that may have a one to onemapping to the port indication of the SRS which may be tied to thecyclic shift, comb, offset, OFDM symbols. The value indicated in the DCIbit indication would map to the ports that may be used for SRStransmission. In one embodiment, one port may be used such as port o. Inanother embodiment, multiple ports may be used (e.g., two ports may beused for SRS transmission). The field may be referred to as antennaports and number of layers for SRS and a fixed number of bits may beused in the DCI to indicate it. This DCI bit indication may be referredto as a spatial domain resource assignment (SDRA).

In another embodiment, the access node transmits configurationinformation of a plurality of SRS resources to a UE. The configurationinformation includes a plurality of SRS resource sets to the UE, eachSRS resource set comprising one or more SRS resources. The access nodethen transmits to the UE, an indication of one of the plurality of SRSresource set.

The antenna ports to be used for SRS transmission may be determinedaccording to an ordering of the SRS ports specified by the predefinedconfiguration. The predefined configuration may be represented bytables. The number of bits, which are indicated in the DCI as defined bythe group arrangements, indicates the ports of transmission which aretied to physical resources such as cyclic shift, comb, OFDM symbols,offset, etc.

In the situation where a group DCI is used to convey the SRSconfiguration, the indication of the layers or ports assigned for a UEwithin the pre-defined SRS port resources is possible. As an example,for each cell (e.g., sector, transmission point, etc.), a predefinednumber of SRS port resources is assigned, such as, 8 or 12 ports, forexample. In the group DCI, the network indicates the layers or portsassigned for a UE within the predefined SRS port resources. For example,the network has configured a SRS resource for all active UEs in thecell, and the SRS resource has the same 8 ports. The group DCI indicateswhich of the 8 ports are allocated for the particular UE. Thepre-defined SRS port resources may be specified in a technical standardspecification, or signaled from the network to the UE via a RRCconfiguration signaling, a MAC signaling, and in some embodiments, aDCI. For example, the RRC signaling configures the SRS port resourceswith indexes 0˜7 as being assigned for UE1 as UE1's SRS ports 0˜7, SRSport resources with indexes 0˜7 as being assigned for UE2 as UE2's SRSports 0˜7, SRS port resources with indexes 8˜15 as being assigned forUE3 as UE3's SRS ports 0˜7, SRS port resources with indexes 8˜15 asbeing assigned for UE4 as UE4's SRS ports 0˜7, etc.

This design can also be adopted for UE-specific DCI (such as DCI format1-1, an enhancement of 1-1 (which is discussed in detail below), etc.)for A-SRS triggering. The DCI may have an antenna port indication fieldfor the A-SRS, which (in some embodiments) may also be used for antennaport indication for PDSCH, and the UE maps the ports indicated in thefield to the pre-defined SRS port resources assigned to the UE. Forexample, UE1 may receive an enhanced DCI of DCI format 1-1 with theantenna port indication field for both PDSCH and SRS indicating value 25(as in Table 7.3.1.2.2-2 of TS 38.212 v16.2.0, (shown below); fordmrs-Type=1, maxLength=2, which are also signaled to the UE for PDSCH)which corresponds to PDSCH DMRS ports 2 and 6 as well as SRS ports 2 and6, which is further mapped to SRS port resources 2 and 6. For anotherexample, UE3 may receive an enhanced DCI of DCI format 1-1 with theantenna port indication field for both PDSCH and SRS indicating value 25which corresponds to PDSCH DMRS ports 2 and 6 as well as SRS ports 2 and6, which is further mapped to SRS port resources 10 and 14.

TABLE 7.3.1.2.2-2 from of TS 38.212 v16.2.0: Antenna port(s) (1000 +DMRS port), dmrs-Type = 1, maxLength = 2 One Codeword: Two Codewords:Codeword 0 enabled, Codeword 0 enabled, Codeword 1 disabled Codeword 1enabled Number of Number of DMRS CDM Number of DMRS CDM Number ofgroup(s) DMRS front-load group(s) DMRS front-load Value without dataport(s) symbols Value without data port(s) symbols 0 1 0 1 0 2 0-4 2 1 11 1 1 2 0, 1, 2, 3, 2 4, 6 2 1 0, 1 1 2 2 0, 1, 2, 3, 2 4, 5, 6 3 2 0 13 2 0, 1, 2, 3, 2 4, 5, 6, 7 4 2 1 1 4-31 reserved reserved reserved 5 22 1 6 2 3 1 7 2 0, 1 1 8 2 2, 3 1 9 2 0-2 1 10 2 0-3 1 11 2 0, 2 1 12 20 2 13 2 1 2 14 2 2 2 15 2 3 2 16 2 4 2 17 2 5 2 18 2 6 2 19 2 7 2 20 20, 1 2 21 2 2, 3 2 22 2 4, 5 2 23 2 6, 7 2 24 2 0, 4 2 25 2 2, 6 2 26 20, 1, 4 2 27 2 2, 3, 6 2 28 2 0, 1, 4, 5 2 29 2 2, 3, 6, 7 2 30 2 0, 2,4, 6 2 31 Reserved Reserved Reserved

As an example, consider a communication system with 4 UEs, the networkmay assign the first port for a first UE, two subsequent ports for thesecond UE, etc. In another embodiment, the network may reuse DMRS portmapping or CSI-RS port mapping.

In one embodiment, the SRS resource is configured for all resource blockgroups (RBGs) but the scheduling or group DCI allows different UEs bescheduled on different RBGs.

The UE identifiers are used to reduce DCI signaling overhead. In anembodiment, to further reduce DCI size, unique but short UE identifiersare assigned to the prescheduled UEs. Instead of using long UEidentifiers, such as a radio network temporary identifier (RNTI), whichmay be 10 or more bits long, short UE identifiers that are unique withinthe prescheduled UEs are assigned to each prescheduled UE. As anexample, if there is a maximum of 16 prescheduled UEs, then the short UEidentifier may be as short as 4 bits, while if there is a maximum of 8prescheduled UEs, then the short UE identifier may be as short as 3bits. In an embodiment, the short UE identifier may be allocated by theaccess node and signaled to the prescheduled UEs using RRC messaging,MAC CE messaging, higher layer messaging, and so on.

The UE identifiers of the prescheduled UEs may be indicated in the DCI.The access node may send a DCI trigger to the prescheduled UEs. Theindication of the prescheduled UEs may be included in a dedicated fieldof the DCI. Additionally, the UE identifiers and the UE identifier fieldin the DCI may be configured using higher layer signaling.

With the use of UE identifiers, prescheduled UEs are able to decode theDCI that is identified using the UE identifier. Those prescheduled UEsthat are able to decode the DCI identified with their UE identifiers areconsidered to be the triggered UEs. UEs which are configured but nottriggered may also attempt to decode the DCI, but these UEs would failbecause the DCI is not addressed to them, and hence they are nottriggered UEs.

As new UEs are prescheduled or additional sets of active UEs arepresent, the UE identifiers may be renewed and reconfigured, possiblythrough higher layer configuration, for example.

As discussed previously, there may be an association between the SRS andthe DL Reference Signals. In order for a UE to receive precoded (orunprecoded) CSI-RS, the UE needs to know which CSI-RS ports have beenallocated, therefore, a CSI-RS port indication needs to be sent to theUE. After the UE receives the CSI-RS port indication, the UE may be ableto infer (from the CSI-RS port indication, for example) thepreconfigured CSI-RS ports to use to measure the downlink channel andthe SRS ports to transmit the SRS because the SRS resource and CSI-RSresource are already preconfigured and there is an association betweenthe SRS and the CSI-RS resources.

Similarly, a UE needs to know which of DMRS ports have been allocatedfor it. A DMRS port indication needs to be sent to the UE. After the UEreceives the DMRS port indication, the UE may be able to infer (from theDMRS port indication, for example) the preconfigured DMRS ports to useto measure the downlink channel and the SRS ports to transmit the SRSbecause the SRS resource and DMRS resource are already preconfigured andthere is an association between the SRS and DMRS resources.

In one embodiment, the SRS indication field which is used to signal thespecific arrangement of SRS resources or ports is also used to indicateto the UE a mapping between the uplink and downlink ports (such as DMRSor CSI-RS ports). Because the SRS ports of each UE are identified, theUE may infer the associated ports in the downlink from the configuration(e.g., the mapping). In such a case, the associated relationship betweenthe uplink and downlink ports may be configured through higher layerconfiguration. A fixed mapping may be defined that can identify theassociation, for example, a one to one mapping between the uplink anddownlink ports may be configured. In another embodiment, a permutationbetween the uplink and downlink ports may be applied as a mapping. Thepermutation may be specified in a technical standard, by an operator ofthe communication system, or through collaboration between the networkand the UE. Hence, the permutation is known by both the network and theUE. As the UE determines the SRS ports or layers indicated to the UE,the UE may measure the corresponding CSI-RS or DMRS for channelestimation and use the measurement to determine the precoder forprecoding of the uplink SRS.

In one embodiment, the indication is implicit. In this case, signalingthe SRS resources or ports may be sufficient to signal the associationdue to the fixed mapping between the resources. In another embodiment,the indication is explicit. In this case, a dedicated field thatexplicitly identifies the downlink CSI-RS, or DMRS for the scheduled UEsmay be used.

DCI may have dedicated field to indicate the DMRS-SRS association. Itmay also have field to indicate the CSI-RS-DMRS association. A table maybe defined in the specification that has a one to one mapping of theuplink port with the downlink ports, for example.

The number of bits used to indicate the association between the downlinkport(s) and SRS port(s) may be used for indication of the transmissionof one of more downlink ports and the SRS ports which may be indicatedby the SRS resources or ports indication fields.

In an embodiment the association is used to indicate not only the portassociation but also the bandwidth association (e.g., the active BWP).

In addition to the above mentioned parameters (e.g., UE identifier, anassociation, and the SRS resources indication), the Group DCI mayinclude some or all of the following:

-   -   A resource allocation field that indicates the time and        frequency resources (resource block groups for UEs, for        example),    -   An explicit indication of CSI-RS or DMRS ports using dedicated        fields in the DCI that may signal the downlink ports. The        explicit indication may also be used by the UE to determine the        rank of the transmission. In an embodiment, the UE may infer the        rank of transmission in the uplink based on the downlink        reception.    -   A transmit power command used for SRS transmission power        control.

FIGS. 4 and 5 illustrate diagrams 400 and 500 of RGBs 405, 407, 505, and507, and example mapping of SRS resources and ports. Diagram 400illustrates RGBs 405 and 407 in a communication system with thefollowing configuration: assume DMRS type 1 (8 ports per RGB per cellfor all paired UEs); in another embodiment 12 port DMRS may beconsidered, and the 8 ports are associated with 8 SRS port resources,selected from n available port resources (e.g., for comb 4, n=48, andfor comb 2, n=16). The SRS port resources may be arranged in a mannersimilar to those illustrated for RBG1 405 and RBG2 407, and each portresource may be assigned with a global index such as (2, 9) representing(COMB shift=2, cyclic shift=₉), i.e., the global indexing may be thesame for different RBGs, or (1, 2, 9) representing (RBG=1, COMB shift=2,cyclic shift=₉), i.e., RBG specific indexing. In some embodiments,instead of RBGs, other time or frequency resource groups can be used,such as (RBG, OFDM symbol), PRB, every 4 RBGs, etc. The SRS fromneighboring cells should be multiplexed on the n SRS port resources. Inorder to indicate, to a UE, which 1, 2, or 4 SRS port resources out ofthe available n SRS port resources would require more bits thanavailable in a DCI message.

Diagram 500 illustrates RGBs 505 and 507, with the same configuration asdiscussed in FIG. 4 . In an embodiment, UE-group CSI-RS or DMRS designis applied to the SRS. For each cell, there are only 8 predefined SRSport resources (shown in FIG. 5 as different shaded and patterned blocksin the SRS port resources region of the RGBs). Then, in a DCI message(such as a group DCI message or a UE-specific DCI message), the layer orport assignments for a UE are made within the 8 predefined SRS portresources and indicated accordingly. As an example, configure a SRSresource for all active UEs in cell 1 (shown as unshaded blocks in theSRS port resources region of the RGBs of FIG. 5 ), and the SRS resourcehas the same 8 ports. That is, SRS port(s) indicated to a UE configuredwith the SRS port resources will be mapped to the SRS port resource(s)in a one-to-one fashion. The group DCI message indicates which of the 8ports are allocated to a particular UE. As an example, rank [1, 2, 4, 1]are signaled for UEs 1, 2, 3, and 4, respectively, without needing toindicate the layer index.

As another example, the DMRS port mapping of the resources are used. TheSRS resource is configured for all RGBs, but the scheduling or group DCIallows different UEs to be scheduled on different RGBs. In anembodiment, a UE (or a cell) is assigned with SRS port resources notconsecutive as shown in FIG. 5 , that is, a UE in CELL1 may not beassigned with COMB shift=1 and cyclic shifts from 1 to 12. Instead, theports resources for the UE is distributed (spread out) in the figure,such as (COMB shift=1, cyclic shift=1), (COMB shift=1, cyclic shift=7),(COMB shift=2, cyclic shift=1), (COMB shift=2, cyclic shift=7), (COMBshift=3, cyclic shift=1), (COMB shift=3, cyclic shift=7), (COMB shift=4,cyclic shift=1), and (COMB shift=4, cyclic shift=7). An advantage isthat the ports for one UE or one cell are more spread out over thepotential SRS port resources, reducing the potential interference oroverlap between cyclic shifts that are close to each other.

Alternative designs to the Group DCI for signaling control informationof the SRS are possible. In one embodiment, the UEs identified in aGroup DCI share a resource allocation field (e.g., Type 0 or Type 1indication). Such a case may occur in a multi-user multiple inputmultiple output (MU-MIMO) setting, where UEs may share resource blocksor RBGs. In this situation, preconfigured UEs which are not prescheduledhave fields in the Group DCI with trigger set to zero.

In another embodiment, the UEs identified in a Group DCI have separatefields for the indication of the resource allocation fields for each ofthe UEs. In this case, preconfigured UEs which are not prescheduled havefields with trigger set to zero.

In any of the preceding embodiments, a UE identifier may be used toidentify prescheduled UEs. In this way, only prescheduled UE are able todecode the DCI. However, any UE may attempt to decode the DCI to checkif it is triggered (prescheduled) or not. For example, all UEs detectingthe DCI can attempt to decode the DCI.

In any of the preceding embodiments, the DCI includes a combination offields listed or subset of the fields aforementioned.

In another embodiment, a modified DCI format, such as DCI format 0_1 (ULGrant) or DCI format 1_1, may be used to dynamically configure triggered(i.e., prescheduled UEs) with the SRS parameters aforementioned and theassociated downlink PDSCH or CSI-RS parameters.

Any of the 5G NR DCI designs may be used to signal the necessaryaforementioned fields, such as the necessary fields added or modified tothe DCI.

FIG. 6 illustrates a diagram 600 of messages exchanged by communicatingdevices performing interference probing. Diagram 600 displays messagesexchanged by an access node 605 and UEs 610 and 612 as the communicatingdevices perform interference probing (may also be referred to astraining or BIT).

UEs 610 and 612 transmit uplink SRSs (blocks 615 and 617). The uplinkSRSs may be unprecoded and periodic, for example. The uplink SRSs aretransmitted to access node 605. Access node 605 estimates the uplinkchannels (block 620). The estimation of the uplink channels is made inaccordance with the uplink SRSs transmitted by the UEs. Access nodepreschedules UEs (block 625). The prescheduling of the UEs may be inaccordance with the signal quality measures, CQI, PMI, or feedback, asdiscussed previously. In the example shown in FIG. 6 , UEs 610 and 612are also the prescheduled UEs. Although the example shown in FIG. 6illustrates the situation where both UEs transmitting uplink SRSs areprescheduled by the access node, in general, a subset of the UEstransmitting uplink SRSs are prescheduled by the access node.

Access node 605 transmits control information configuring uplink SRSsfor the prescheduled UEs (block 630). The control information may betransmitted in group DCI or unicast DCI, for example. The group DCI maycontain the UE identifiers of the prescheduled UEs in one embodiment.The control information may include (a subset thereof is also possible)configuration information for UEs, such as, transmission bandwidth ofthe uplink SRS, or a portion of the transmission bandwidth, anindication of the transmission ports of the uplink SRS, an indication ofthe SRS resources or ports of the uplink SRS, an implicit or explicitindication of the cyclic shift and comb, the subbands of the uplink SRS,SRS trigger, CSI-RS trigger, DMRS trigger, a mapping between the CSI-RSand SRS, an indication of the mapping between the DMRS and SRS, etc.

If access node 605 is to transmit CSI-RS, access node 605 transmits theCSI-RS (block 635). UEs 610 and 612 may perform downlink channelestimation (blocks 640 and 642). The downlink channel estimation may beperformed in accordance with the CSI-RS transmitted by access node 605.If access node 605 does not transmit the CSI-RS, UEs 610 and 612 may notperform downlink channel estimation. If access node 605 does transmitthe CSI-RS, one or both of UEs 610 and 612 (as well as other UEs servedby access node 605) may perform downlink channel estimation. In otherwords, not all UEs served by access node 605 perform downlink channelestimation, even with access node 605 transmitting the CSI-RS.

UEs 610 and 612 transmit uplink SRS (blocks 645 and 647). The uplink SRSare transmitted in accordance with the configuration informationtransmitted by access node 605. The uplink SRS may be precoded, e.g.,single value decomposition (SVD) based precoder is used to precode theuplink SRS. Access node 605 determines interference covariance matrices(block 650). The interference covariance matrices are determined basedon the uplink SRS transmitted by UEs 610 and 612 (i.e., the prescheduledUEs). Access node 605 determines downlink precoders (block 655). Thedownlink precoders are determined in accordance with the interferencecovariance matrices. Access node 605 transmits downlink data to UEs 610and 612 (block 660). Access node 605 precodes the downlink data for eachprescheduled UE using the downlink precoder associated with theprescheduled UE, for example. The precoded downlink data is transmittedover a physical downlink shared channel (PDSCH), for example.

In the 3GPP 5G NR standards related to existing DCI formats, the DCIsize is minimized in order to reduce communications overhead. As anexample, in the DCI format 2_3, used for transmitting group transmitpower control (TPC) commands for SRS transmissions by one or more UEs,the DCI size is less than or equal to the DCI size of DCI format 1_0.Therefore, the number of bits available to transmit the uplink SRSconfigurations is limited. However, existing DCI formats do not supportdynamic signaling of SRS configuration. Additionally, controlinformation has to be provided for all configured UEs, even those thatare not triggered (i.e., UEs other than the prescheduled UEs) totransmit the uplink SRS, therefore, the number of UEs configured usingthe existing DCI formats is limited due to the limitation of the numberof bits.

According to an example embodiment, a DCI format for conveying SRSconfiguration information is provided. In an embodiment, the DCIincludes SRS configuration information only for the prescheduled UEs.Existing DCI formats include control information for all configured UEs,even those that are not prescheduled. Having the DCI include only SRSconfiguration information for the prescheduled UEs reduces the size ofthe DCI, thereby permitting a reduction in the DCI size or an inclusionof more SRS configuration information in the same sized DCI.

FIG. 7 illustrates a first example DCI 700. DCI 700, as shown in FIG. 7, is an example of a DCI where the DCI includes SRS configurationinformation for only prescheduled UEs and a short UE identifier is usedto identify the UEs. DCI 700 includes an identifier field 705, whichidentifies the DCI being a DCI for conveying SRS configurationinformation to prescheduled UEs. DCI 700 also includes SRS configurationinformation for each of the prescheduled UEs, such as first prescheduledUE 710, second prescheduled UE 712, and N-th prescheduled UE 714.

As an example of the savings achievable by using the short UEidentifiers and conveying information only for the prescheduled UEs,consider a situation where an access node is serving 20 UEs, with only 5prescheduled UEs. If 10 bit long RNTIs are used, the DCI format wouldneed to convey at least 20*10=200 bits of identifying information alone,while using the short UE identifiers and prescheduled UEs, DCI format700 would need to convey only 5*4=20 bits of identifying information.

For first prescheduled UE 710, DCI 700 includes a UE ID field 720, aresource allocation field 722, a SRS TPC command field 724, and a SRSindication field 726. UE ID field 720 comprising the short UE identifierof the prescheduled UE, and may be 4 bits in size, for example. DCI 700includes similar information for other prescheduled UEs. Resourceallocation field 722 indicates time and frequency resource blocks orgroups for first prescheduled UE 710. The size of resource allocationfield 722 may depend upon the type of the resource allocation, as wellas the BWP size, with the size also being dependent on the Resourceallocation type, for example. SRS TPC command field 724 comprises apower control command for the SRS, and may be 2 bits in size, forexample. SRS indication field 726 indicates SRS resources, SRS ports,SRS transmission bandwidth, etc. The value in SRS indication field 726may be preconfigured with a set of different possible arrangements ofSRS resources or ports, SRS transmission bandwidth, etc., values andonly an index to a particular set of possible SRS resources, SRS ports,SRS transmission bandwidth, etc., is held in SRS indication field 726 toreduce size. SRS indication field 726 may also be used to indicate themapping with the DL ports (layers, reference signals, etc.). An exampleSRS indication field 726 size is 4 bits. SRS indication field 726supports SRS port indication in the uplink to transmit the SRS. Alsoimplicitly indicated is the SRS cyclic shift, SRS subband, SRS comb,etc. Also implicitly indicated is the precoded CSI-RS port(s) assignedto first prescheduled UE 710 in the downlink (e.g., the same ports). Theexample sizes of the various fields of DCI 700 are for discussionpurposes only. The example embodiments presented herein are operablewith other field sizes, arrangements, or configurations.

As related to resource allocation fields, such as resource allocationfield 722, Resource Type 1 may be used for frequency allocation.Alternatively, Resource Type 2 may be used for frequency allocation.Resource block groups may be used for UEs. Additionally, the frequencyallocation may include the allocation for the SRS transmission.

As related to downlink antenna ports, an indication for the UE may beused for downlink ports or downlink layers. As an example, theindication may be a bitmap with each bit of the bitmap corresponding toa downlink antenna port or group of downlink antenna ports. As anotherexample, the indication may be a value. A UE may be able to determineCSI-RS or DMRS ports to use in accordance with the SRS ports allocatedto the UE. As an example, the indication may use the SRS indicationfield. In another embodiment, the indication of the SRS ports may use abitmap with each bit of the bitmap corresponding to a downlink antennaport or group of SRS ports.

In an embodiment, information associated with configured UEs that arenot prescheduled are not included in DCI format 700. A prescheduled UEmay process the DCI to determine if the access node has triggered theprescheduled UE for SRS transmission, for example.

In an embodiment, to further reduce DCI size, the SRS configurationinformation for each prescheduled UE is arranged in order (e.g.,increasing or decreasing order) so that it is not necessary to includethe short UE identifier in the DCI. Therefore, additional reduction inthe DCI size is achieved.

In an embodiment, time and frequency resource blocks or groups areconfigured for the prescheduled UEs. In FIG. 7 , each prescheduled UEmay be configured with a different allocation of time and frequencyresource blocks or groups. In this embodiment, a single allocation oftime and frequency resource blocks or groups is configured for theprescheduled UEs indicated in the DCI. In an embodiment, a single DCI isused to convey SRS configuration information for the prescheduled UEs ofthe access node. In such a situation, the DCI includes SRS TPC commandand SRS indication for each prescheduled UE. The SRS TPC command and SRSindication for each prescheduled UE may be arranged in accordance withthe short UE identifier assigned to each prescheduled UE. The SRS TPCcommand and SRS indication for each prescheduled UE may be arranged inincreasing short UE identifier or decreasing short UE identifier, forexample.

In an embodiment, a single DCI is used to convey SRS configurationinformation for a subset of the prescheduled UEs of the access node. Insuch a situation, the DCI includes SRS TPC command and SRS indicationfor each prescheduled UE in the subset. As an example, a first DCIincludes SRS TPC commands and SRS indications for a first subset of theprescheduled UEs, a second DCI includes SRS TPC commands and SRSindications for a second subset of the prescheduled UEs, and so on. TheSRS TPC command and SRS indication for each prescheduled UE in a subsetmay be arranged in accordance with the short UE identifier assigned toeach prescheduled UE in the subset. The SRS TPC command and SRSindication for each prescheduled UE in the subset may be arranged inincreasing short UE identifier value or decreasing short UE identifiervalue, for example.

FIG. 8 illustrates a second example DCI 800. DCI 800, as shown in FIG. 8, is an example of a DCI where there is a single allocation of time andfrequency resource blocks or groups is configured for the prescheduledUEs. DCI 800 includes an identifier field 805, which identifies the DCIbeing a DCI for conveying SRS configuration information to prescheduledUEs, and a resource allocation field 810. Resource allocation field 810comprising time and frequency resource blocks or groups for theprescheduled UEs indicated in DCI 800. DCI 800 also includes SRS TPCcommands and SRS indications for each of the prescheduled UEs, such asfirst prescheduled UE 815, second prescheduled UE 817, and N-thprescheduled UE 819.

For first prescheduled UE 815, DCI Boo includes a SRS TPC command field825, and a SRS indication field 827. SRS TPC command field 825comprising a power control command for the SRS, and may be 2 bits insize, for example. SRS indication field 827 comprising SRS resources,SRS ports, SRS transmission bandwidth, etc. The value in SRS indicationfield 827 may be preconfigured with a set of possible SRS resources, SRSports, SRS transmission bandwidth, etc., values and only an index to aparticular set of possible SRS resources, SRS ports, SRS transmissionbandwidth, etc., is held in SRS indication field 827 to reduce size. Anexample SRS indication field 827 size is 4 bits. SRS indication field827 supports SRS port indication in the uplink to transmit the SRS. Alsoimplicitly indicated is the precoded CSI-RS port(s) assigned to theprescheduled UE in the downlink (e.g., the same ports). Also implicitlyindicated is the SRS cyclic shift, SRS subband, SRS comb, offset, etc.

In an embodiment, to further reduce DCI size, allocations of time andfrequency resource blocks or groups are configured for the prescheduledUEs. The allocation of time and frequency resource blocks or groups maybe configured for the prescheduled UEs that are scheduled for SRStransmission. Hence, in such a situation, allocations of time andfrequency resource blocks or groups are included for each prescheduledUE that is scheduled for SRS transmission and omitted for eachprescheduled UE that is not scheduled for SRS transmission.

FIG. 9 illustrates a third example DCI 900. DCI 900, as shown in FIG. 9, is an example of a DCI where there are allocations of time andfrequency resource blocks or groups for each prescheduled UE that isscheduled for SRS transmission. DCI 900 includes an identifier field905, which identifies the DCI being a DCI for conveying SRSconfiguration information to prescheduled UEs. DCI 900 also includesinformation for each prescheduled UE, such as first prescheduled UE 910,second prescheduled UE 912, and N-th prescheduled UE 914. Theinformation may differ depending on the prescheduled UE, e.g.,prescheduled UEs that are scheduled for SRS transmission versusprescheduled UEs that are not scheduled for SRS transmission.

For each prescheduled UE that is scheduled for SRS transmission, such asfirst prescheduled UE 910, DCI 900 includes a resource allocation field920, a SRS TPC command field 922, and a SRS indication field 924.Resource allocation field 920 comprising time and frequency resourceblocks or groups for the prescheduled UE. The size of resourceallocation field 920 may depend upon the type of the resourceallocation, as well as the BWP size, and may be 10 bits in size, forexample. SRS TPC command field 922 comprising a power control commandfor the SRS, and may be 2 bits in size, for example. SRS indicationfield 924 comprising SRS resources, SRS ports, SRS transmissionbandwidth, etc. The value in SRS indication field 924 may bepreconfigured with a set of possible SRS resources, SRS ports, SRStransmission bandwidth, etc., values and only an index to a particularset of possible SRS resources, SRS ports, SRS transmission bandwidth,etc., is held in SRS indication field 924 to reduce size. An example SRSindication field 924 size is 4 bits. SRS indication field 924 supportsSRS port indication in the uplink to transmit the SRS. Also implicitlyindicated is the precoded CSI-RS port(s) assigned to the prescheduled UEin the downlink (e.g., the same ports). Also implicitly indicated is theSRS cyclic shift, SRS subband, SRS comb, etc. The example sizes of thevarious fields of DCI 900 are for discussion purposes only. The exampleembodiments presented herein are operable with other field sizes.

For each prescheduled UE that is not scheduled for SRS transmission,such as N-th prescheduled UE 914, resource allocation field 930, SRS TPCcommand field 932, and SRS indication field 934 are set to zero or someother specified value. Although FIG. 9 illustrates an example where N-thprescheduled UE 914 is a prescheduled UE that is not scheduled for SRStransmission, any of the N prescheduled UE in DCI 900 may be aprescheduled UE that is not scheduled for SRS transmission.

The example embodiments illustrated in FIGS. 7-9 are for group DCI.However, the example embodiments presented herein are also operable forunicast DCI. In unicast DCI, the DCI is specifically addressed to asingle UE. The addressing of the DCI to a particular UE may beaccomplished by encoding the DCI with an identifier of the UE. When theDCI is encoded using the identifier of the UE, only the UE will be ableto decode the DCI, while other UEs will detect the encoded DCI as noise.Because the DCI is specifically addressed to the UE using itsidentifier, the DCI does not need to include a unique identifier of theUE. Thereby, the size of the DCI is reduced.

FIG. 10 illustrates a fourth example DCI 1000. DCI 1000, as shown inFIG. 10 , is an example of a DCI used in unicast DCI. DCI 1000 includesan identifier field 1005, a resource allocation field 1010, a SRS TPCcommand field 1015, and a SRS indication field 1020. Identifier field1005 identifies the DCI being a DCI for conveying SRS configurationinformation to prescheduled UEs. Resource allocation field 1010comprising time and frequency resource blocks or groups for theprescheduled UE. The size of resource allocation field 1010 may dependupon the type of the resource allocation, as well as the BWP size, andmay be 10 bits in size, for example. SRS TPC command field 1015comprising a power control command for the SRS, and may be 2 bits insize, for example. SRS indication field 1020 comprising SRS resources,SRS ports, SRS transmission bandwidth, etc. The value in SRS indicationfield 1020 may be preconfigured with a set of possible SRS resources,SRS ports, SRS transmission bandwidth, etc., values and only an index toa particular set of possible SRS resources, SRS ports, SRS transmissionbandwidth, etc., is held in SRS indication field 1020 to reduce size. Anexample SRS indication field 1020 size is 4 bits. SRS indication field1020 supports SRS port indication in the uplink, and indicates SRS portsto use to transmit the SRS. Also implicitly indicated is the precodedCSI-RS port(s) assigned to the prescheduled UE in the downlink (e.g.,the same ports). Also implicitly indicated is the SRS cyclic shift, SRSsubband, SRS comb, offset, etc. The example sizes of the various fieldsof DCI 1000 are for discussion purposes only. The example embodimentspresented herein are operable with other field sizes.

In another embodiment, dynamic signaling using a field (or fields) inthe DCI may be used to signal an identifier of a reference downlinkresource (or resources). A dedicated field to signal the mapping from aconfigured fixed mapping may be configured using higher layer signaling.

FIG. 11 illustrates a flow diagram of example operations 1100 occurringin a UE participating in interference probing and receives downlinkdata. Operations 1100 may be indicative of operations occurring in a UEas the UE participates in interference probing and receives downlinkdata. The UE may be a prescheduled UE.

Operations 1100 begin with the UE transmitting an uplink SRS (block1105). The uplink SRS may be unprecoded. The uplink SRS may be periodicin nature. The UE receives DCI from an access node (block 1107). The DCImay include SRS configuration information for the UE. The SRSconfiguration information configures the UE to make a SRS transmission.The DCI may also include CSI-RS configuration. The DCI may be part of agroup DCI message. The DCI may be a unicast DCI message. The UE mayestimate the downlink channel (block 1109). The UE estimates thedownlink channel using a CSI-RS transmitted by the access node. The UEtransmits a precoded SRS (block 1111). The precoded SRS is transmittedin accordance with the SRS configuration information received in theDCI. The UE receives downlink data (block 1113). The downlink data isreceived from the access node. The downlink data is precoded using aprecoder determined in accordance with the precoded SRS transmitted bythe UE.

FIG. 12 illustrates a flow diagram of example operations 1200 occurringin an access node participating in interference probing and receivesdownlink data. Operations 1200 may be indicative of operations occurringin an access node as the access node participates in interferenceprobing and transmits downlink data.

Operations 1200 begin with the access node estimating an uplink channel(block 1205). The access node estimates the uplink channel using a SRStransmitted by a UE, for example. The SRS may be precoded or unprecoded.The access node preschedules UEs (block 1207). The access nodepreschedules UEs in accordance with the SRSs transmitted by UEs. As anexample, the access node preschedules UEs associated with SRSs withsignal quality exceeding a specified threshold. The access nodetransmits DCI to the prescheduled UEs to trigger SRS transmission (block1209). The DCI transmitted by the access node may also cause the UE tomeasure downlink CSI-RS or DMRS. The access node configures SRSs for theprescheduled UEs and sends SRS configuration information to theprescheduled UEs in the DCI. The SRS configuration information may alsoinclude CSI-RS information. The DCI may be a group DCI or unicast DCIs.

The access node may transmit a CSI-RS (block 1211). The CSI-RS may beused for downlink channel estimation. The access node receives aprecoded SRS (block 1213). The precoded SRS may be received inaccordance with the SRS configuration information. The access nodedetermines an interference covariance matrix (block 1215). Theinterference covariance matrix is determined in accordance with theprecoded SRS. The access node determines a downlink precoder (block1217). The downlink precoder is determined in accordance with theinterference covariance matrix. The access node transmits downlink data(block 1219). The downlink data is precoded in accordance with thedownlink precoder.

FIG. 13 illustrates a flow diagram of example operations 1300 occurringin an access node configuring uplink SRSs. Operations 1300 may beindicative of operations occurring in an access node as the access nodeconfigures uplink SRSs and receives an uplink SRS transmission.

Operations 1300 begin with the access node transmitting a SRSconfiguration (block 1305). The SRS configuration may be transmitted indownlink control information, e.g., in a group DCI or a unicast DCI. Inthe situation when the group DCI is used, the group DCI may be addressedto UEs (e.g., prescheduled UEs) using UE identifiers, which are uniquewithin the group of UEs, but are shorter than typical UE identifiers, inorder to save signaling overhead, for example. In an embodiment, the SRSconfiguration includes information regarding arrangements of SRS portresources (e.g., combs, offsets, cyclic shifts, symbols, etc.) The SRSport resources may also be grouped into plurality of resource groups. Inan embodiment, the SRS configuration includes sets of SRS ports of SRSresources. In an embodiment, the SRS configuration includes informationregarding associations between SRS port resources and downlink portresources (such as CSI-RS ports, DMRS ports, etc.). Also included may beinformation about mappings between the ports.

The access node transmits an indication of SRS resources (block 1305).In an embodiment, the indication of the SRS resources indicates a SRSresource group to use for uplink SRS transmission. In an embodiment, theindication of the SRS resources indicates a subset of the SRS ports ofthe SRS resource to use for uplink SRS transmission. In an embodiment,the indication of the SRS resources indicates an association to use todetermine the SRS ports to use for uplink SRS transmission. Theindication of the SRS resources may be transmitted in downlink controlinformation, e.g., in a group DCI or a unicast DCI. When the group DCIis used, the UE identifiers (as described above) are used. Theindication of the SRS resources may be included in a message transmittedafter the transmission of the SRS configuration. The message includingthe indication of the SRS resources may be the first message transmittedafter the transmission of the SRS configuration. The access nodereceives uplink SRS (block 1309). The uplink SRS is received inaccordance with the SRS resources as indicated.

FIG. 14 illustrates a flow diagram of example operations 1400 occurringin a UE transmitting uplink SRSs. Operations 1400 may be indicative ofoperations occurring in a UE as the UE receives an uplink SRSconfiguration and transmits an uplink SRS.

Operations 1400 begin with the UE receiving a SRS configuration (block1405). The SRS configuration may be received in downlink controlinformation, e.g., in a group DCI or a unicast DCI. In the situationwhen the group DCI is used, the group DCI may be addressed to UEs (e.g.,prescheduled UEs) using UE identifiers, which are unique within thegroup of UEs, but are shorter than typical UE identifiers, in order tosave signaling overhead, for example. In an embodiment, the SRSconfiguration includes information regarding arrangements of SRS portresources (e.g., combs, offsets, cyclic shifts, symbols, etc.). The SRSport resources may also be grouped into plurality of resource groups. Inan embodiment, the SRS configuration includes sets of SRS ports of SRSresources. In an embodiment, the SRS configuration includes informationregarding associations between SRS port resources and downlink portresources (such as CSI-RS ports, DMRS ports, etc.). Also included may beinformation about mappings between the ports. Even if the UE is not anintended recipient of the SRS configuration, the UE receives thedownlink control information and attempts to decode the downlink controlinformation.

The UE receives an indication of SRS resources (block 1407). In anembodiment, the indication of the SRS resources indicates a SRS resourcegroup to use for uplink SRS transmission. In an embodiment, theindication of the SRS resources indicates a subset of the SRS ports ofthe SRS resource to use for uplink SRS transmission. In an embodiment,the indication of the SRS resources indicates an association to use todetermine the SRS ports to use for uplink SRS transmission. Theindication of the SRS resources may be received in downlink controlinformation, e.g., in a group DCI or a unicast DCI. When the group DCIis used, the UE identifiers (as described above) are used. Theindication of the SRS resources may be included in a message receivedafter the reception of the SRS configuration. The message including theindication of the SRS resources may be the first message received afterthe transmission of the SRS configuration. The UE transmits the uplinkSRS (block 1409). The uplink SRS is transmitted in accordance with theSRS resources as indicated.

Some embodiments described above for flexible A-SRS triggering for BITmay lead to higher DCI overhead as it contains more bits in the SRSrequest field. In addition, the A-SRS triggering may occur morefrequently, such as each time a MU scheduling occurs. To reduce DCIoverhead, some example embodiments are provided. First, a more flexibleframework to split SRS transmission parameter information among RRCconfiguration signaling, MAC CE, and DCI would be useful. Minimizingstandard impact is achieved by keeping as much SRS transmissionparameter information in RRC and MAC as possible, and the DCI containsonly the minimum parameter information necessary for dynamic signaling.Furthermore, existing DCIs can be enhanced to include new fields and beassociated with new UE behavior.

Example embodiments are provided for group-common DCI based overheadreduction.

BIT sounding is to support PDSCH with MU-MIMO, in which multiple UEs arepaired together in PDSCH transmission and its associated DMRS.Therefore, BIT sounding should “mirror” the PDSCH DMRS. For example, itis known that for the PDSCH DMRS Type 1, at most 8 DMRS ports per RBGper cell can be supported. Correspondingly, 8 SRS port resources can besplit and indicated to a number of UEs, where the SRS port resources arein terms of cyclic shift, comb and shift, and also possibly OFDM symbolsof a RBG of a cell. Then a mapping (i.e., an association) of DL DMRSports to the SRS port resources can be designed and the port informationcan be signaled to the UEs via the SRS trigger. This may be done in anoverhead-efficient way via GC DCI sent to the set of UEs possibly pairedfor MU transmissions in a slot.

The GC DCI can trigger SRS to be sent from multiple UEs at the sametime, i.e., a common triggering offset can be used. In addition, otherfields, such as the CMR or IMR indication, may be included, and thedesign may be similar to a CSI request field as in DCI format 0_1. Anembodiment includes a GC DCI for flexible A-SRS triggering with reducedoverhead, and the GC DCI is sent to a set of UEs possibly paired for MUtransmission in a slot, with a common triggering offset, and each UE isassigned with UE-specific frequency domain resource assignment (FDRA),port allocation (with respect to the UE's serving cell's available SRSport resources, e.g., cyclic shift, comb, offset, and shift), and CMR orIMR indication.

In an embodiment, a new field of A-SRS triggering offset with slotoffset ko and symbol position is included in the GC DCI. In anembodiment, a new field of A-SRS beamforming with dynamically indicatedDL CMR or IMR similar to the CSI request field in DCI format 0_1 isincluded in the GC DCI. In an embodiment, a higher priority for theA-SRS in the GC DCI is assumed by the UE if the A-SRS is assigned with aFDRA and/or port allocation. In an embodiment, the UE-specific portallocation field is replaced by a group-common (joint) port allocationfield for all UEs paired on the RBG (or associated frequency domainunit), by indicating only the ranks (number of layers for a data ornumber of ports for SRS or DMRS) of the paired UEs (the ordering of theUEs may be indicated elsewhere, or UE ID is also included to accompanythe rank allocation). With this example embodiment, the ports of a UEhave to follow a certain pattern such as consecutive or evenly spaced,but as long as the ranks are indicated, each UE can determine its SRSport resources.

Enhancements to DCI 1-1 for SRS probing include:

Field (Item) Bits Reference Notes Frequency Variable Variable withResource Existing for PDSCH. Now domain Allocation Type apply to PDSCHand SRS resource assignment (FDRA) Time domain 4 Carries the row indexof the Existing for PDSCH. No resource items in pdsch_allocationListchange assignment in RRC (TDRA) VRB-to-PRB 0, 1 0 bit if only resourceallocation Existing for PDSCH. Now may mapping type 0 is configured orif also apply to SRS interleaved VRB-to-PRB mapping is not configured byhigh layers; 1 bit according to Table 7.3.1.1.2-33 otherwise, onlyapplicable to resource allocation type 1 PRB bundling 0, 1 0 bit if thehigher layer Existing for PDSCH. Now may size indicator parameterprb-BundlingType also apply to SRS is not configured or is set to‘static’ 1 bit if the higher layer parameter prb-BundlingType is set to‘dynamic’ Antenna 4, 5, 6 Determined by Existing for PDSCH. Now port(s)and dmrs Configuration Type apply to PDSCH and SRS number of and maxLength layers See e.g., Table 7.3.1.2.2-2 of TS 38.212 v16.2.0. SRSrequest 2 or Existing. Now may add more more bits for SRS resourceselection SRS Time 0, 4 Carries the row index of the New. Apply to SRS.Optional. domain items in pdsch_allocationList Shall be earlier thanPDSCH resource or pusch_allocationList or assignment srs_allocationListin RRC. Optional. Default is per RRC configuration SRS TPC 0, 2 Optionalfor SRS power New. Optional. May present command control if SRS hasseparate power control than PUSCH SRS 0~6 Optional, indicate SRS New.Optional. Can reuse 0_1 beamforming beamforming/precoding based CSIRequest field design indicator on a CMR and optionally an IMR. If notpresent then a default CMR is used for SRS beamforming determination . .. Other fields: same as before

Limitations in enhanced DCI 1-1 include:

-   -   Some fields as “Existing for PDSCH. Now may also apply to SRS”.    -   However it is not clear under what condition those PDSCH fields        are also applied to SRS.    -   The DCI does not have a CSI request. However, for BiT with DL        probing to improve the link adaptation, a CSI request is        desired.    -   Furthermore, enhancing UL DCI 0_1 for SRS probing is not        described in much detail.

Embodiments are provided for supporting UE-specific DCI based overheadreduction. To reduce DCI overhead, an embodiment uses DL DCI formats 1_0or 1_1 for both A-SRS triggering and PDSCH scheduling, and the SRS andPDSCH have the same PRB or port allocation. In DCI formats 1_0 or 1_1,there are already fields for: 1) A-SRS trigger, 2) dynamically indicatedPDSCH PRB allocation via a DL FDRA field, 3) dynamically indicated PDSCHports, and 4) possibly a field for a PRB bundling size indicator (as inDCI format 1_1), etc. These fields can be (re)used by the UE for SRStriggering purposes. New fields for BIT purposes are also added, e.g.,SRS resource indication, SRS triggering offset (similar to PDSCH SLIV),a field for a CMR or IMR indication which may be similar to a CSIrequest field as in DCI format 0_1. The UE assumes that the FDRA andports are also applied for the triggered SRS, which can considerablyreduce DCI overhead. For the port indication, a mapping (an association)of DCI DL port indication to SRS ports (in terms of cyclic shift, comband shift) is needed, which can be defined in Release-17.

In an embodiment, UE-specific DCI (e.g., format 1_1) is reused, with theintroduction of new fields for flexible A-SRS triggering with reducedoverhead. In the embodiment, the UE first performs A-SRS transmissionaccording to existing fields of FDRA, port indication, and PRB bundlingsize indicator, as well as the new fields of SRS resource indicator, SRStriggering offset, and CMR/IMR indication. The UE then performs PDSCHreception according to at least the same FDRA and port indication in thesame DCI. In an embodiment, a new field of A-SRS triggering offset withslot offset ko and symbol position is included in the UE-specific DCI.In an embodiment, a new field of A-SRS beamforming with dynamicallyindicated DL CMR and/or IMR similar to the CSI request field in DCIformat 0_1 is included in the UE-specific DCI. In an embodiment, ahigher priority for the A-SRS in the UE-specific DCI is assumed by theUE if the A-SRS is assigned with a FDRA and/or port allocation. In anembodiment, the UE supports more receive antenna ports (e.g., for PDSCHand its DMRS) than transmit antenna ports (e.g., for SRS). For example,the UE can only sound on one port. In this case, the UE shall ignore thePDSCH port indication but just sound on the one port. For anotherexample, the UE can only sound on two port but receive on up to fourports. In this case, the UE can still utilize the PDSCH port indicationinformation, i.e., sound on one port if the PDSCH is only one layer, butsound on the two ports if the PDSCH is two or more layers. In anembodiment, the port indication for SRS is not supported but a rank(number of ports or number of layers) indication is supported. That is,the UE uses the rank indicator for the SRS (or PDSCH) for its SRStransmission. The ports associated with the rank are pre-determinedbased on the standard or RRC configuration.

Embodiments are provided for supporting both UE-specific DCI basedoverhead reduction and GC DCI based overhead reduction, for flexibleA-SRS triggering for interference probing. In an embodiment, the GC DCIis an enhanced GC DCI format 2_3 with UE FDRA and port indication. In anembodiment, the UE-specific DCI is an enhanced DL DCI formats 1_0 or 1_1to reinterpret existing FDRA or port indication fields for SRStransmission. In an embodiment, both above embodiments are supported. Inan embodiment, the enhanced GC DCI or UE-specific DCI are supported andbecome new DL DCI formats. In any embodiment, a new field for A-SRStriggering offset with slot offset ko and symbol position can beincluded. In any embodiment, a new field for A-SRS beamforming withdynamically indicated DL CMR or IMR similar to the CSI request field inDCI format 0_1 can be included. In any embodiment, a higher priority forthe A-SRS is assumed by the UE if the A-SRS is assigned with a FDRA orport allocation.

In an embodiment, the GC DCI or UE-specific DCI are for TDD with ULoperating in OFDM (rather than single carrier FDMA (SC-FDMA)). In orderto properly utilize BIT or SRS probing for the DL, the UL and DL shouldbe as symmetric as possible. Because the DL is only OFDM, it is moresuitable that the UL is also OFDM. This may also be more suitable if thePDSCH or SRS transmissions are not consecutive in the frequency domain,such as with PRB skipping, FDRA type 0 with non-consecutive RBGs,interleaved VRB to PRB mapping, etc.

In an embodiment, the GC DCI or UE-specific DCI reuse the PDSCH TDRAdesign for its SRS triggering offset design. In an embodiment, the GCDCI or UE-specific DCI reuse the PUSCH TDRA for its SRS triggeringoffset design. In an embodiment, the GC DCI or UE-specific DCI reuse thePUSCH or PDSCH TDRA for its SRS triggering offset design, but modify theL value configuration and range so that it fits into SRS transmissions.For example, the network may configure SRS to be only on 8˜14 OFDMsymbols, and hence the current range of L for PUSCH of 4˜14 or 1˜14 maybe modified to 8˜14, so that L value can require fewer bits to indicate.

In an embodiment for the GC DCI or UE-specific DCI include a new fieldof A-SRS beamforming with dynamically indicated DL CMR or IMR. The fieldmay be similar to the CSI request field in DCI format 0_1, or may reusethe same indication or configuration as the CSI request field, forexample. In an embodiment the A-SRS beamforming field is identical tothe CSI request field with 0, 1, 2, 3, 4, 5, or 6 bits determined byhigher layer parameter report TriggerSize. When all the bits of thefield in the DCI are set to zero, the SRS is not beamformed. A non-zerocodepoint of the field in the DCI is mapped to the CMR or IMR associatedwith a CSI triggering state according to the order of the associatedpositions of the up to 2^(N) ^(TS) −1 trigger states inCSI-AperiodicTriggerStateList with codepoint ‘1’ mapped to thetriggering state in the first position, for example. After the UEdetermines the CMR from the field, the CMR's ports are also selected bythe UE according to the antenna port indication field, and the selectedCMR ports and the indicated or associated IMR are used by the UE togenerate the SRS beamforming for each SRS port.

In some embodiments, a flag (or switch, indicator, etc.) is introducedto specify if the A-SRS triggered by a DCI reuses some fields fromanother scheduled or triggered transmission, or not. A purpose of theflag is to make the DCI useful for both BIT purposes and non-BITpurposes with minimum redesign. For example, when the flag is set, theUE shall assume the triggered A-SRS in the DCI reuses a field (e.g.,FDRA) of a PDSCH scheduled by this DCI or another DCI, but when the flagis not set, the UE shall not assume the A-SRS reuses a field of anothertransmission. In other words, the flag serves as an indication to the UEabout assuming an association of A-SRS parameters to anothertransmission or not.

In an embodiment, the flag (or switch, indicator, etc.) is a field in aDCI, that is, the association can be indicated dynamically for fullflexibility. In an embodiment, the flag is turned on or off via a MACCE. In an embodiment, the flag is turned on or off via RRC configurationfor a DCI format.

In an embodiment, the flag is for a DCI that may be used to schedule aPUSCH transmission. An example of this may be DCI format 0_1 or thelike, which schedules the PUSCH and includes fields for PUSCHtransmission such as PUSCH FDRA, antenna port(s), with or withoutfrequency hopping, on UL (e.g., in an uplink carrier) or SUL(supplementary uplink carrier), on which BWP, etc. In an embodiment, theflag is for an association of A-SRS to PUSCH. When the flag is set andan A-SRS is triggered and a PUSCH is scheduled, the UE uses theparameters obtained from some PUSCH fields for the SRS transmission, andthe fields may include at least one or more of PUSCH FDRA, PUSCH antennaport(s) indication, PUSCH frequency hopping, UL or SUL indication, BWPindication, closed-loop TPC command, etc. The PUSCH and A-SRS havedifferent timings so that they would not collide, that is, the A-SRS mayhave its own TDRA, or have an offset relative to the PUSCH (such as nslots earlier than the PUSCH, for example). However, when the flag isnot set and an A-SRS is triggered, the UE does not use those PUSCHfields for the A-SRS transmission.

In an embodiment, the flag is a field associated with the SRS requestfield in the DCI format. In an embodiment, the flag field containsmultiple bits to indicate the UE which PUSCH fields should be used foran associated A-SRS, such as a bit for A-SRS reusing PUSCH FDRA/BWP ornot, and a bit for A-SRS reusing PUSCH TPC command or not, etc. In anembodiment, the flag is for an association of A-SRS to PDSCH. When theflag is set and an A-SRS is triggered, the UE uses the parametersobtained from some PDSCH fields for the SRS transmission, and the fieldsmay include at least one or more of a PDSCH FDRA, a PDSCH antennaport(s) indication, a PDSCH frequency hopping, a BWP indication, aPRB-to-VRB interleaving, etc. However, when the flag is not set and anA-SRS is triggered, the UE does not use those PDSCH field for the A-SRStransmission. The associated PDSCH is not scheduled with this DCI, butthe association is specific to the UE so that the UE can link to thecorrect PDSCH. The linking to the correct PDSCH may be achieved via acommon ID used for the SRS and PDSCH (e.g., a field with a ID, or theDCI RNTI, etc.) or via their timing relation (e.g., triggered at thesame time, triggered within 2 slots, PDSCH scheduled n slot after theA-SRS, n being 1, 2, etc.).

In an embodiment, the flag is for a DCI that may be used to schedule aPDSCH transmission. An example of this may be DCI format 1_1 or thelike, which schedules the PDSCH and includes fields for PDSCHtransmission such as PDSCH FDRA, antenna port(s), PRB bundling size,etc. In an embodiment, the flag is for an association of A-SRS to thePDSCH of the same DCI. When the flag is set and an A-SRS is triggeredand a PDSCH is scheduled, the UE uses the parameters obtained from somePDSCH fields for the SRS transmission, and the fields may include atleast one or more of a PDSCH FDRA, a PDSCH antenna port(s) indication, aPDSCH PRB bundling size, etc. However, when the flag is not set and anA-SRS is triggered, the UE does not use those PDSCH field for the A-SRStransmission. In an embodiment, the flag is a field associated with theSRS request field in the DCI format. In an embodiment, the flag fieldcontains multiple bits to indicate the UE which PDSCH fields should beused for an associated A-SRS, such as a bit for A-SRS reusing PDSCH FDRAor BWP or not, and a bit for A-SRS reusing PDSCH antenna ports or not,etc.

In an embodiment, the DCI that may schedule the PUSCH or PDSCH, ortrigger A-SRS may also have a CSI request field. The flag or a bit ofthe flag indicates to the UE whether the A-SRS is also associated withthe CSI request field. When the flag is set, the UE may use the CMR andoptionally the IMR associated with the CSI request for the A-SRSbeamforming. The DCI may be an extension of format 0_1 or 1_1, forexample. In the embodiment of DCI with PDSCH scheduling, SRS triggering,and CSI request, the A-SRS may be tied to the scheduled PDSCH (reusingPDSCH FDRA, for example) or the CSI request (reusing the CMR/IMR forbeamforming). The CSI request may be associated with an aperiodic CSI-RStransmission. This can be especially useful for BIT because one DCIindicates the DL RS for the A-SRS beamforming, the A-SRS parametersshared with the PDSCH, and the PDSCH. The DL RS can also be used for DLprobing for MCS adjustment, i.e., the UE reports a CQI but not a PMI tothe access node so that the access node can perform link adaptation forthe PDSCH.

In an embodiment, an uplink DCI (e.g., DCI format 0_1) that may schedulea PUSCH indicates that no PUSCH is scheduled via the UL-SCH indicator,i.e., UL-SCH bit is zero. The fields that are designed for PUSCH can beredefined for A-SRS triggering parameters. For example, one or more bitsmay be used for A-SRS triggering offset or TDRA, one or more bits may beused for A-SRS port indication, one or more bits may be used for A-SRSFDRA, and so on.

In an embodiment, a downlink DCI (e.g., DCI format 1_1) that mayschedule a PDSCH indicates that no PDSCH is scheduled. The no-PDSCH maybe indicated via a DL-SCH indicator, i.e., DL-SCH bit is zero, or may beindicated via setting one or more bits in the original PDSCH fields tobe zero, such as the Downlink assignment index bits, FDRA/TDRA bits,etc. The fields that are designed for PUSCH can be redefined for A-SRStriggering parameters. For example, one or more bits may be used forA-SRS triggering offset or TDRA, one or more few bits may be used forA-SRS port indication, one or more few bits may be used for A-SRS FDRA,and so on.

In summary, UL DCI may be used for SRS trigger with or without PUSCH,with or without CSI request, with the SRS tied to PUSCH (e.g., FDRA,etc.) or not tied to PUSCH, with the SRS tied to PDSCH or not tied toPDSCH, with the SRS tied to the CSI request field or not tied to the CSIrequest field. DL DCI may be used for SRS trigger with or without PDSCH,with or without CSI request, with the SRS tied to PDSCH (e.g., FDRA,etc.) or not tied to PDSCH, with the SRS tied to the CSI request fieldor not tied to the CSI request field.

Embodiments are provided for GC DCI to trigger SRS. An embodimentenhances the current GC DCI format 2_3. The enhanced DCI format 2_3 doesnot have a FDRA field to reduce overhead. The DCI may include multipleSRS blocks, each may be used to trigger one or more SRS transmissions.Each block includes a SRS request field (optional), one or more SRS TPCcommand fields if the block can trigger multiple SRS transmissions. Theblocks may be for the same UE or multiple UEs. Each of the UEs thatreceives a SRS trigger in a block in the DCI assumes reception ofanother DCI with FDRA, and use that FDRA for the triggered SRS. Theother DCI may be a UL DCI, e.g., DCI format 0_1, enhanced DCI formats0_1 or 0_1, or so on, in which case the FDRA and possibly other fieldssuch as BWP indication, UL or SUL indication, frequency hoppingindication, antenna port indication, etc., are also used by the UE forthe A-SRS transmission. The other DCI may be a DL DCI, e.g., DCI format1_1, enhanced DCI formats 1_1 or 1_0, or so on, in which case the FDRAand possibly other fields such as antenna port indication, PRB bundlingsize indication, etc., are also used by the UE for the A-SRStransmission.

In an embodiment, each UE's block in the GC DCI is associated with aflag (or switch, indicator, etc.), and when the flag is set, the UE usesa linked DCI's field for the A-SRS, and when the flag is not set, the UEdoes not look for a linked DCI's field for the A-SRS. The flag may be afield in the GC DCI, may be activated or deactivated via MAC CE, or maybe configured via RRC signaling. The linked DCI is specific to the UE sothat the UE can link to the correct DCI (which may be achieved via acommon ID used for the SRS and PDSCH (e.g., a field with a ID, or theDCI RNTI, etc.) or via their timing relation (e.g., triggered at thesame time, triggered within 2 slots, PDSCH scheduled n slot after theA-SRS, n being 1, 2, etc.)). In an embodiment, the GC DCI does not haveto be for paired UEs only. Each UE's block and the fields within theblock are pre-configured via RRC signaling, and when a UE's SRS requestfield has all the bits set to 0, no SRS is triggered for that UE, andwhen a UE's SRS request field is set to not all 0, A-SRS is triggered.

In an embodiment, in a GC DCI, a same TDRA field is used for all thetriggered SRS in GC DCI. That is, each UE does not have a UE-specificTDRA field, which saves overhead. In an embodiment, in a GC DCI, a fewchoices of TDRAs are provided for all the UEs using the DCI, and eachTDRA is associated with an ID. Then in each UE's block, a field is usedto indicate to the UE which one of the TDRAs that the UE shall applybased on the ID. In an embodiment, individual TDRA fields are configuredfor each SRS block, that is, each SRS triggered may be associated with adifferent TDRA. In an embodiment, the SRSs triggered by the DCI aretransmitted at the same slot but possibly in different OFDM symbols.Then the DCI includes a group-common TDRA field (e.g., ko for slotoffset) that applies to all the triggered SRS from this DCI, and anindividual TDRA field (e.g., OFDM symbol location, SLIV, etc.) for eachSRS block.

SRS coverage may be limited by the transmission power of the UE if theDL coverage for the UE is not an issue. To overcome the powerlimitation, the following embodiments are provided.

An embodiment focuses the power on the narrower bandwidth or fewersubcarriers to increase the UL receive SNR. Current sounding alreadysupports non-wideband transmissions (4 RBs at the minimum, for example),but in a coverage-limited scenario, the narrowband sounding may befurther split into multiple partial soundings to cover the bandwidth ofone narrowband sounding. Narrowband sounding is also useful in takingadvantage of frequency selectivity and reducing interference between SRSfrom different UEs. In addition, narrowband sounding also improves thefrequency-selective precoding by SRS.

To support partial bandwidth sounding, the standards may allow 1-2 PRBsounding, PRB skipping, larger comb (i.e., RE skipping), etc.

However, an issue that may arise from partial bandwidth sounding is thatthe access node may not be able to combine multiple partial bandwidthsounding transmissions to obtain wideband CSI, because each soundingtransmission is generally associated with an unknown random phase. Thisneeds to be addressed.

An embodiment repeats the sounding in the time domain, includingmultiple symbols in the same slot and across multiple slots. Simplerepetition can be supported. Repetition with a different comb or combshift or (staggered in REs or PRBs or with different densities) may alsobe allowed.

An embodiment is to allow time domain orthogonal cover codes (TD-OCC) inSRS. In the transmission of the CSI-RS, TD-OCC is supported so thatmultiple OFDM symbols can be utilized to strengthen CSI-RS transmission.This can also be adopted in SRS.

In order to increase SRS capacity, embodiments should allow more UEs tosound at the same time, and allow more sounding opportunities orresources as well as SRS transmissions multiplexed with other signals.

An embodiment uses less time or frequency resources for each SRStransmission. If each SRS transmission occupies fewer subcarriers orOFDM symbols, then more UEs can sound and SRS capacity is increased. Forexample, SRS comb may be increased to 8 or 12. For another example, PRBskipping or narrower bandwidth for SRS may be considered, which can alsoimprove SRS coverage described above.

An embodiment allows non-orthogonal low-correlation sequences to beused. In general, the number of orthogonal sequences for SRS is limited.To allow more SRS transmissions be multiplexed on overlapping time orfrequency resources, non-orthogonal low-correlation sequences may beadopted. The network can configure or trigger the transmission ofnon-orthogonal sequences when needed, such as when SRS capacity becomesa limiting factor for operations, but can still use only orthogonalsequences at other times.

An embodiment allows more time or frequency resources to be used by SRS.For example, all 14 symbols in a UL slot may be used for SRS, which isalready supported in NR-U. To provide this flexibility, flexibleconfiguration and triggering of SRS need to be standardized. This alsomotivates flexible A-SRS triggering to dynamically or opportunisticallyutilize unused UL symbols or PRBs or even DL symbols or PRBs in TDD. Tosupport the latter, a SRS switching gap (due to RF retuning, forexample) similar to SRS carrier-based switching may be used for harvestsome unused DL symbols, i.e., the UE switches from DL reception to SRStransmission on one or several OFDM symbols according to networkconfiguration or indication after a SRS switching gap, and switches backto DL reception after the SRS transmission and another SRS switchinggap. Additionally, concurrent SRS and PUCCH transmission or even SRS andPUSCH transmission may be considered to allow more SRS opportunities.

In 3GPP Release 17, further enhanced MIMO (FeMIMO) sounding referencesignal enhancements include:

-   -   Identify and specify enhancements on aperiodic SRS triggering to        facilitate more flexible triggering or DCI overhead or usage        reduction;    -   Specify SRS switching for up to 8 antennas (e.g., xTyR, x={1, 2,        4} and y={6, 8});    -   Evaluate and, if needed, specify the following mechanism(s) to        enhance SRS capacity or coverage: SRS time bundling, increased        SRS repetition, partial sounding across frequency, and so on.

Motivations regarding flexible triggering include:

-   -   Limited triggering info in the DCI (1, 2, or 3 bits only);    -   Inflexible triggering delay;    -   Vital roles of the SRS in DL full MIMO CSI acquisition, BM, UL        frequency diversity and MIMO support, etc.;    -   Vital roles of an A-SRS in TDD cooperative MIMO via DL        interference probing and mitigation include:        -   UE to Tx SRS according to DL (pre-)scheduling results, so            that the access node can estimate DL interference and then            mitigate DL interference via precoder adjustment,        -   Some similarity with DL non-zero power (NZP) CSI-RS based            interference probing for better modulation and coding scheme            (MCS). This is also after scheduling and before PDSCH, but            with UL SRS for better precoding (hence bi-directional            training, BIT).    -   Also closely related to SRS coverage or capacity enhancements.

FIG. 15 illustrates an example one-shot BIT operation flow 1500. BIToperation flow 1500 involves an access node 1505 and paired UEs 1510. InBIT, precoded SRSs (transmitted by paired UEs 1510) is based on PDSCHscheduling and then the PDSCH itself. The precoded sounding is based onMU pre-scheduling allowing access node 1505 to cooperatively probe theDL interference conditions in the UL.

As shown in FIG. 15 , Covariance(Y) (block 1515) captures inter/intracell interference in UL and the (Cov(Y))⁻¹h (block 1517) enables ULinterference avoidance. Then, by reciprocity, DL Tx with this precodingenables cooperative DL interference avoidance. Theoretical guidance isderived from global optimization, for example. In 5G NR, SRS used forreciprocity-based CSI acquisition is configured as “SRS for antennaswitching”.

FIGS. 16A and 16B illustrate communication systems 1600 and 1650highlighting example interference conditions. Communication system 1600of FIG. 16A illustrates a situation where UL SRS transmissions made byUE 1605, using transmit beamforming results in weak interference at afirst access node 1607, while a second access node 1609 sees stronginterference. Communication system 1650 of FIG. 16B illustrates asituation where beamforming may be used to reduce interference to UEs. Afirst access node 1657 can use beamforming in the direction of UE 1655,but a second access node 1659 avoids beamforming in the direction of UE1655 because such transmissions may cause high interference at UE 1655.

As related to flexible A-SRS triggering for BIT:

-   -   The SRS may include enhancements with dynamically indicated        parameters associated with corresponding DL transmissions. They        may include:        -   A-SRS triggering with dynamically indicated PRB allocation            (e.g., FDRA) and port allocation,        -   A-SRS triggering with dynamically indicated DL CMR or IMR,        -   A-SRS triggering with flexible triggering delay.

As related to reducing DCI overhead for flexible triggering, motivationsinclude:

-   -   Presence of the flexible triggering may lead to higher DCI        overhead; and    -   BiT may also require more A-SRS triggers.

Example embodiments may include:

-   -   UE-specific DCI for A-SRS with FDRA and port indication (same as        PDSCH). However, FDRA may require 5˜19 bits in general, and port        indication may require 4˜6 bits.    -   Group common DCI to a set of UEs possibly paired for MU        transmission in a slot, with FDRA and port indication. However,        SRS triggering offsets may not be equal for the set of UEs.

According to an example embodiment, methods and apparatus forconfiguration of the SRS transmissions with all the needed SRSparameters in DCI but with reduced DCI overhead, as well as theassociated UE assumptions, behaviors, or configurations to support thisare provided. Table 1 presents the existing DCI 1-1 format used forscheduling of PDSCH in a single cell. Table 2 presents antenna ports fora variety of DMRS types in 3GPP TS 38.212. The existing DCI format doesnot indicate SRS transmission parameters (other than the 2-bit SRSrequest), and the SRS triggered by the SRS request is transmitted basedon parameters pre-configured in RRC configuration signaling for SRS,e.g., SRS-config.

TABLE 1 Current DCI 1-1 format used for scheduling of PDSCH in one cell.Field (Item) Bits Reference Carrier indicator 0, 3 Identifier for DCI 1Always set to 1, indicating a DL DCI format formats Bandwidth partindicator 0, 1, 2 Frequency domain Variable Variable with ResourceAllocation Type resource assignment Time domain resource 4 Carries therow index of the items assignment in pdsch_allocationList in RRCVRB-to-PRB mapping 0, 1 0 bit if only resource allocation type 0 isconfigured or if interleaved VRB-to-PRB mapping is not configured byhigh layers; 1 bit according to Table 7.3.1.1.2-33 otherwise, onlyapplicable to resource allocation type 1 PRB bundling size 0, 1 0 bit ifthe higher layer parameter prb-BundlingType is indicator not configuredor is set to ‘static’ 1 bit if the higher layer parameterprb-BundlingType is set to ‘dynamic’ Rate matching indicator 0, 1, 2 Bitsize is determined by higher layer parameters rateMatchPatternGroup1 andrateMatchPatternGroup2. ZP CSI-RS Trigger 0, 1, 2 Modulation and coding5 scheme [TB1] New data indicator [TB1] 1 Redundancy version 2 [TB1]Modulation and coding 5 scheme [TB2] New data indicator [TB2] 1Redundancy version 2 [TB2] HARQ process number 4 Downlink assignment 0,2, 4 4 bits if more than one serving cell are configured in the index DLand the higher layer parameter pdsch-HARQACK- Codebook = dynamic, wherethe 2 MSB bits are the counter DAI and the 2 LSB bits are the total DAI;2 bits if only one serving cell is configured in the DL and the higherlayer parameter pdsch-HARQ-ACKCodebook = dynamic, where the 2 bits arethe counter DAI; 0 bits otherwise. TPC command for 2 scheduled PUCCHPUCCH resource 2 indicator PDSCH-to- 0, 1, 2, 3 Row number(index) of K1HARQ_feedback timing Number of bit is determined by log2(I). ‘I’ is thenumber indicator of elements in the IE PUCCH-Config.dl-DataToUL-ACKAntenna port(s) and 4, 5, 6 Determined by dmrs Configuration Type andmax number of layers Length. See the table to the right. Transmission 0,3 0 bit if higher layer parameter tci-PresentInDCI is not configurationindication enabled; 3 bits otherwise (See QCL page) SRS request 2 CBGtransmission 0, 2, 4, 6, 8 information(CBGTI) CBG flushing out 0, 1information(CBGFI) DMRS sequence 1 initialization

TABLE 2 Antenna ports. dmrs-Type maxLength Bit Field Length Table in38.212 1 1 4 Table 7.3.1.2.2-1 1 2 5 Table 7.3.1.2.2-2 2 1 5 Table7.3.1.2.2-3 2 1 6 Table 7.3.1.2.2-4

According to an example embodiment, a further enhanced DCI 1-1 format isprovided. The enhanced DCI 1-1 format supports the scheduling of PDSCHin one cell, as well as associated SRS probing. Table 3 presents detailsregarding an example enhanced DCI 1-1 format usable for schedulingPDSCHs in a single cell and associated SRS probing. With theenhancement, the DCI format can also indicate SRS transmissionparameters for the SRS transmission triggered by the SRS request field,i.e., the SRS transmission reuses some PDSCH transmission parameters andignore the corresponding SRS transmission parameters pre-configured inRRC signaling if the SRS association with the PDSCH is set to a specificvalue, but the SRS transmission still use SRS transmission parameterspre-configured in RRC signaling otherwise. When the SRS association withthe PDSCH is set to the specific value, the resulting SRS transmissionis based on some parameters configured in SRS-config (e.g., SRS comb,sequence, etc.) and other parameters indicated for the co-scheduledPDSCH (e.g., FDRA, etc.); otherwise the resulting SRS transmission isbased on parameters configured/indicated for SRS but not on parametersindicated for the PDSCH.

TABLE 3 Example enhanced DCI 1-1 format used for scheduling PDSCH in onecell and associated SRS probing. Field (Item) Bits Reference NotesFrequency Variable Variable with Resource Existing for PDSCH. Now domainresource Allocation Type apply to PDSCH and SRS assignment (FDRA) Timedomain 4 Carries the row index of the Existing for PDSCH. No resourceitems in pdsch_allocationList in change assignment RRC (TDRA) VRB-to-PRB0, 1 0 bit if only resource allocation Existing for PDSCH. Now mappingtype 0 is configured or if may also apply to SRS interleaved VRB-to-PRBmapping is not configured by high layers; 1 bit according to Table7.3.1.1.2-33 otherwise, only applicable to resource allocation type 1PRB bundling 0, 1 0 bit if the higher layer Existing for PDSCH. Now sizeindicator parameter prb-BundlingType is may also apply to SRS notconfigured or is set to ‘static’ 1 bit if the higher layer parameterprb-BundlingType is set to ‘dynamic’ Antenna port(s) 4, 5, 6 Determinedby Existing for PDSCH. Now and number of dmrs Configuration Type andapply to PDSCH and SRS layers max Length See e.g., Table 7.3.1.2.2-2 ofTS 38.212 v16.2.0. SRS request 2 or Existing. Now may add more more bitsfor SRS resource selection SRS Time 0, 4 Carries the row index of theNew. Apply to SRS. domain resource items in pdsch_allocationList orOptional. Shall be earlier assignment pusch_allocationList or than PDSCHsrs_allocationList in RRC. Optional. Default is per RRC configurationSRS TPC 0, 2 Optional for SRS power control New. Optional. May presentcommand if SRS has separate power control than PUSCH SRS 0~6 Optional,indicate SRS New. Optional. Can reuse beamforming beamforming/precodingbased 0_1 CSI Request field indicator on a CMR and optionally an designIMR. If not present then a default CMR is used for SRS beamformingdetermination SRS association 0, 1 Optional. If set, then A-SRS uses Newwith PDSCH PDSCH fields such as FDRA. CSI request 0~6 Optional. Triggersan aperiodic New CSI report. May also trigger an aperiodic CSI-RS/CSI-IMtransmission. SRS association 0, 1 Optional. If set, then A-SRS uses Newwith the CSI CSI-RS/CSI-IM associated with request the CSI requestfields for beamforming. . . . Other fields: same as before

In an embodiment, the enhanced DCI 1-1 format includes the followingbeneficial features:

-   -   The FDRA field and the antenna port(s) indications field support        SRS probing, but the overhead is high. The enhanced DCI 1-1        design reuses the existing FDRA and antenna port indications        fields in the associated PDSCH-scheduling DCI, and adds a new        SRS triggering offset, so that a single DCI can be used for two        operations (SRS transmissions and PDSCH reception, for example).    -   The GC DCI may also add a new SRS triggering offset field, so        that all SRSs are transmitted on overlapping resources for BiT        purposes.

FIG. 17 illustrates a diagram 1700 of information exchanged between anaccess node 1705 and a UE 1707 as access node 1705 configures UL SRSsounding and then makes a DL transmission based on the UL SRS soundingresults. Access node 1705 transmits the configuration of the SRS ports(event 1710). The transmission is made to UE 1707. The configuration ofthe SRS ports includes the mapping to the SRS port resources. Accessnode 1705 transmits the DCI (event 1712). The DCI includes the SRSrequest and the PDSCH scheduling. UE 1707 transmits the A-SRS inaccordance with the DCI (event 1714). The A-SRS may be transmitted inaccordance with the FDRA or port indication, as well as the SRStriggering offset included in the DCI, for example.

TABLE 4 Example of Enhanced DCI 0-1 format used for scheduling PUSCH inone cell and associated SRS probing. Field Bits Reference NoteIdentifier for DCI 1 Existing for formats PUSCH Carrier indicator 0 or 3Existing for PUSCH. Now may apply to SRS as well UL/SUL 0, 1 0 - bit forUE not configured with Existing for Indicator SUL in the cell PUSCH. Nowmay 1 - bit for UEs configured with SUL in apply to SRS as the cell wellBandwidth part 0, 1, 2 Determined by BandwidthPart- Existing forindicator Config in higher layer message and PUSCH. Now may 38.212 -Table 7.3.1.1.2-1 apply to SRS as well Frequency Variable Variable withResource Allocation Existing for domain resource Type PUSCH. Now mayassignment apply to SRS as well Time domain 4 Carries the row index ofthe items Existing for resource in pusch_allocationList in RRC PUSCH.Now may assignment Number of Bit Length is determined apply to SRS as bylog(I, 2), where I is the number of well but with elements in puschallocationList in certain offset RRC Frequency 0, 1 Existing for HoppingFlag PUSCH. Now may apply to SRS as well Modulation and 5 38.214 - 6.1.4Existing for coding scheme PUSCH. New data 1 Existing for indicatorPUSCH. Redundancy 2 0, 1, 2, 3 Existing for version PUSCH. HARQ process4 Existing for number PUSCH. TPC command 2 Existing for for scheduledPUSCH. Now may PUSCH apply to SRS as well SRS resource VariableDetermined by RRC Parameter SRS- Existing for indicator SetUse PUSCH.Now may apply to SRS as well Precoding 0, 2, 3, 4, 5, 6 Determined byulTxConfig, Number Existing for information and of Antenna ports,PUSCH-tp, PUSCH. Now may number of layers ULmaxRank apply to SRS as(TPMI) well Antenna ports 2, 3, 4, 5 Determined by PUSCH-tp, DL-Existing for DMRS-config-type, DL-DMRS- PUSCH. Now may config-max-len,Rank apply to SRS as well SRS request 2 Table 7.3.1.1.2-24 Existing forPUSCH. Now may include more bits and more information CSI request 0, 1,2, 3, 4, 5, 6 Determined by ReportTriggerSize in Existing for RRCmessage. PUSCH. Now may See Configure Aperiodic Trigger apply to SRS assection for the details. well for beamforming SRS Time domain 0~4Carries the row index of the items New. Apply to resource inpdsch_allocationList or SRS. Optional. assignment pusch_allocationListor Shall be earlier srs_allocationList in RRC. Optional. than PDSCHDefault is per RRC configuration SRS TPC 0, 2 Optional for SRS powercontrol New. Optional. command May present if SRS has separate powercontrol than PUSCH SRS association 0, 1, or more Optional. If set, thenA-SRS uses New with PDSCH/PUSCH PDSCH fields such as FDRA, or anassociated PDSCH's fields such as FDRA SRS association 0, 1 Optional. Ifset, then A-SRS uses CSI- New with the CSI RS/CSI-IM associated with theCSI request request fields for beamforming. UL-SCH 1 0 - UL-SCH shallnot be transmitted Indicator on the PUSCH 1 - UL-SCH shall betransmitted on the PUSCH

Not all the new fields or optional fields need to be present in EnhancedDCI 0-1 format.

As shown in FIG. 17 , the A-SRS transmission may also be made inaccordance with the carrier indicator field, BWP indicator field,VRB-PRB mapping field, PRB bundling size field, TPC command for thePUCCH field, or TPC command for the SRS field in the DCI. Furthermore,the SRS triggering offset may be indicated in a TDRA field (reuseddesign from PUSCH or PDSCH, for example). A CMR, and optionally an IMR,may be included for UE 1707 to determine the SRS precoding, which mayreuse the design of CSI request field, for example.

Example SRS mapping of resources and ports may be as follows(referencing FIG. 4 ):

-   -   Assume that DMRS Type 1, i.e., 8 ports, RBG, or cell for all        paired UEs, is used.    -   The 8 ports are associated with 8 SRS port resources, selected        from n available port resources, such as:        -   For comb 4, n=48,        -   For comb 2, n=16.    -   The SRS from neighboring cells should be multiplexed on the n        SRS port resources,    -   Then, to indicate to a UE which 1, 2, or 4 SRS port resources        out of the available n SRS port resources would require too many        bits.

FIG. 18 illustrates diagrams 1800 of RGBs 1805 and 1807 with an examplemapping of SRS resources and ports. In an embodiment, the UE-groupCSI-RS or DMRS design is applied to the SRS design. As an example, foreach cell, restrict the cell to only a specified number (e.g., 8, butother values are possible) of pre-defined SRS port resources. Then, inthe group DCI, indicate the layers or ports for a UE from the specifiednumber (e.g., 8) of pre-defined SRS port resources. For example,configure a SRS resource for all active UEs in cell 1 with all SRSresources having the same 8 ports. The group DCI indicates which of the8 ports are for a particular UE. For example, rank [1, 2, 4, 1] aresignaled for UE 1, 2, 3, 4. There is no need to indicate the layerindex. For another example, reuse DMRS port mapping. As another example,the SRS resource may be configured for all RBGs, but the scheduling orgroup DCI allows different UEs to be scheduled on different RBGs.

According to an example embodiment, an enhanced DL DCI 1-1 format isprovided. The enhanced DL DCI 1-1 format supports the scheduling ofPDSCH with associated SRS probing. As an example if a SRS associationwith PDSCH field is set to a specified value, then an associated SRS isbased on PDSCH parameters (e.g., the FDRA), while if the field is notset to the specified value, then the associated SRS is based on RRCparameters. As another example, if a CSI request field is set to a firstspecified value and a SRS association with CSI request field is set to asecond specified value, then an associated SRS is based on CSIparameters, while if the fields are not set to the first and secondspecified values, then the associated SRS is based on RRC parameters.Table 5 presents details regarding an example enhanced DL DCI 1-1 formatusable for scheduling PDSCHs and CSIs, along with associated SRSprobing. Similar embodiments can also be provided for other DL DCIformats, such as format 1-2 and so on.

TABLE 5 Example DL DCI 1-1 format for SRS association with CSI andPDSCH. Field (Item) Bits Reference SRS association 0, 1 Optional. Ifset, then A-SRS uses PDSCH fields with PDSCH such as FDRA. CSI request0~6 Optional. Triggers an aperiodic CSI report. May also trigger anaperiodic CSI-RS/CSI-IM transmission. SRS association 0, 1 Optional. Ifset, then A-SRS uses CSI-RS/CSI- with the CSI IM associated with the CSIrequest fields for request beamforming.

According to an example embodiment, an enhanced UL DCI 0-1 format isprovided. The enhanced UL DCI 0-1 format supports the scheduling ofPUSCH with associated SRS probing. The enhancements to UL DCI 0-1 formatmay be similar to the enhancements to DL DCI 1-1 format to support thescheduling of PDSCH and CSI with associated SRS probing. In the UL, theSRS is associated with PUSCH and transmit power control (TPC) commands.Table 6 presents details regarding an example enhanced UL DCI 0-1 formatusable for scheduling PUSCHs and TPC command, along with associated SRSprobing. Similar embodiments can also be provided for other UL DCIformats, such as format 0-2 and so on.

TABLE 6 Example enhanced UL DCI 0-1 format for scheduling PUSCH and CSIand associated SRS probing Field Bits Reference Identifier for DCI 1formats Carrier indicator 0 or 3 UL/SUL Indicator 0, 1 0 - bit for UEnot configured with SUL in the cell 1 - bit for UEs configured with SULin the cell Bandwidth part 0, 1, 2 Determined by BandwidthPart-Configindicator in higher layer message and 38.212 - Table 7.3.1.1.2-1Frequency domain Variable Variable with Resource Allocation Typeresource assignment Time domain 4 Carries the row index of the itemsresource in pusch_allocationList in RRC assignment Number of Bit Lengthis determined by log(I, 2), where I is the number of elements inpusch_allocationList in RRC Frequency 0, 1 Hopping Flag TPC command for2 scheduled PUSCH SRS resource Variable Determined by RRC Parameter SRS-indicator SetUse Precoding 0, 2, 3, 4, 5, 6 Determined by ulTxConfig,Number of information and Antenna ports, PUSCH-tp, ULmaxRank number oflayers (TPMI) Antenna ports 2, 3, 4, 5 Determined by PUSCH-tp, DL-DMRS-config-type, DL-DMRS-config-max-len, Rank SRS request 2 Table7.3.1.1.2-24 CSI request 0, 1, 2, 3, 4, 5, 6 Determined byReportTriggerSize in RRC message. See Configure Aperiodic Triggersection for the details. SRS Time domain 0~4 Carries the row index ofthe items resource in pdsch_allocationList or assignmentpusch_allocationList or srs_allocationList in RRC. Optional. Default isper RRC configuration SRS TPC 0, 2 Optional for SRS power controlcommand SRS association 0, 1, or more Optional. If set, then A-SRS useswith PDSCH/PUSCH PUSCH fields such as FDRA, or an associatedPDSCH/PUSCH's fields such as FDRA SRS association 0, 1 Optional. If set,then A-SRS uses CSI- with the CSI RS/CSI-IM associated with the CSIrequest request fields for beamforming.

As shown in Table 6, enhancements to the UL DCI 0-1 format include:

-   -   a carrier indicator indicating a carrier conveying the PUSCH,        and it may also apply to the SRS if triggered and if the A-SRS        is indicated by the field of SRS association with PDSCH/PUSCH to        use the PUSCH's fields;    -   a UL or SUL indicator indicating the UE using the UL or SUL for        the PUSCH if being configured with a SUL, and it may also apply        to the SRS similar to the above interpretation/behavior for the        carrier indicator field;    -   a BWP indicator indicating a BWP conveying the PUSCH, and it may        also apply to the SRS similar to above;    -   a FDRA indicating a FDRA for the PUSCH, and it may also apply to        the SRS similar to above;    -   a TDRA indicating a TDRA for the SRS based on RRC signaling;    -   a frequency hopping flag indicating utilization of frequency        hopping for the PUSCH, and it may also apply to the SRS similar        to above;    -   a SRS resource indicator indicating a SRS resource used for        conveying the SRS;    -   antenna ports indicator indicating antenna ports used to convey        the PUSCH, and it may also apply to the SRS similar to above;    -   a PUSCH TPC command indicating PUSCH power control, and it may        also apply to the SRS similar to above;        -   a SRS request indicator indicating a request for SRS            transmission;    -   a CSI request indicator indicating a request for CSI        transmission;    -   a SRS TDRA indicating a TDRA for SRS based on RRC signaling;    -   a SRS TPC command indicating SRS power control;    -   a SRS association with PDSCH or PUSCH indicating use of PDSCH or        PUSCH parameters for SRS transmission; or    -   a SRS association with a CSI request indicating use of CSI        parameters for SRS transmission.

In an embodiment, the flag (or switch, indicator, etc.) is a field in aDCI, that is, the association can be indicated dynamically for fullflexibility. In an embodiment, the flag is turned on or off via a MACCE. In an embodiment, the flag is turned on or off via RRC configurationfor a DCI format.

In an embodiment, UL DCI may be used for SRS trigger with or withoutPUSCH, with or without CSI request, with the SRS tied to PUSCH (e.g.,FDRA, etc.) or not tied to PUSCH, with the SRS tied to PDSCH or not tiedto PDSCH, with the SRS tied to the CSI request field or not tied to theCSI request field. DL DCI may be used for SRS trigger with or withoutPDSCH, with or without CSI request, with the SRS tied to PDSCH (e.g.,FDRA, etc.) or not tied to PDSCH, with the SRS tied to the CSI requestfield or not tied to the CSI request field.

According to an example embodiment, SRS enhancements for operation infrequency range 1 (FR1) and frequency range 2 (FR2) are provided. TheSRS enhancements facilitate flexible SRS triggering, with DCI overheador usage reduction. As an example, SRS switching for a plurality ofantennas (e.g., 8 antennas->xTyR, with x=1, 2, 4 and y=6, 8, where T isthe number of transmit antennas and R is the number of receiveantennas).

FIG. 19A illustrates a flow diagram of example operations 1900 occurringin a UE communicating (e.g., transmitting or receiving) a referencesignal based on a reference signal association flag. Operations 1900 maybe indicative of operations occurring in a UE as the UE communicates(e.g., transmits or receives) a reference signal (e.g., transmitting aSRS or receiving a CSI-RS) based on a reference signal association flag.The reference signal association flag may be received from an accessnode serving the UE, for example. The reference signal association flagmay be received in a DCI message, a MAC CE, or a configuration RRCsignaling.

Operations 1900 begin with the UE receiving a DCI message scheduling aDL transmission (block 1905). The DCI message includes a referencesignal trigger, and in some embodiments, a reference signal associationflag. As discussed previously, the reference signal association flag mayindicate (based on the indicated value) that the UE should transmit (orreceive) a reference signal (e.g., the SRS, the CSI, etc.) in accordancewith parameters signaled to the UE in a DCI message (which may be thesame DCI message or a different DCI message) for another purpose. As anexample, based on the reference signal association flag, the UE mayutilize the PDSCH parameters signaled in a DCI message (e.g., in a DLDCI message that schedules the PDSCH) or CSI request parameters signaledin a DCI message for the reference signal transmission. The PDSCHparameters that are also applicable to the reference signal transmissionmay include frequency-domain parameters (e.g., FDRA, PRB locations,etc.), spatial-domain parameters, and so on. In an embodiment, in thesituation where the UE uses the CSI request parameters to transmit thereference signal, the DCI message also includes a CSI request. Asanother example, based on the reference signal association flag, the UEmay utilize pre-defined parameters, e.g., parameters signaled in RRCconfiguration signaling, i.e., even if the DCI message schedules a PDSCHand also triggers a reference signal transmission, the flag may indicatethat the reference signal transmission does not reuse any co-scheduledPDSCH parameters, and instead, the reference signal transmission usesparameters configured for the reference signal. The DCI(s) in thisembodiment (as well as in other embodiments) are just an example; thedesign can also be extended to other types of control informationmessages such as MAC CE and RRC signaling.

The UE performs a check to determine if the reference signal associationflag is set to a specified value (block 1907). If the reference signalassociation flag is set to the specified value, the UE communicates(transmits or receives) the reference signal (e.g., the SRS, the CSI,etc.) in accordance with parameters signaled to the UE in a DCI messagefor another purpose (block 1909). If the reference signal associationflag is not set to the specified value, the UE communicates (transmitsor receives) the reference signal in accordance with parameters signaledto the UE in a RRC message based on pre-configuration configuring thereference signal (block 1911).

FIG. 19B illustrates a flow diagram of example operations 1950 occurringin an access node communicating (receiving or transmitting) a referencesignal based on a reference signal association flag for a referencesignal trigger transmitted in a DCI message. Operations 1950 may beindicative of operations occurring in an access node as the access nodecommunicates (receives or transmits) a reference signal (e.g., a SRS orCSI-RS) based on a reference signal association flag. The referencesignal association flag may be transmitted by the access node servingthe UE, for example. The reference signal association flag may betransmitted in a DCI message, a MAC CE, or a configuration RRCsignaling.

Operations 1950 begin with the access node transmitting a DCI message(block 1955). The DCI message may be transmitted to a UE, multiple UEs,or a group of UEs. The DCI message includes a reference signal trigger,and in some embodiments, a reference signal association flag. Asdiscussed previously, the reference signal association flag may indicate(based on the indicated value) that the UE should transmit or receive areference signal (e.g., the SRS, the CSI, etc.) in accordance withparameters signaled to the UE in a DCI message (which may be the sameDCI message or a different DCI message) for another purpose. As anexample, based on the reference signal association flag, the UE mayutilize the PDSCH parameters signaled in a DCI message or CSI requestparameters signaled in a DCI message. In an embodiment, in the situationwhere the UE uses the CSI request parameters to transmit the referencesignal, the DCI message also includes a CSI request. As another example,based on the reference signal association flag, the UE may utilizeparameters based on pre-configuration signaled in RRC signalingconfiguring the reference signal. The access node communicates (receivesor transmits) the reference signal (block 1957). The reference signalbeing received or transmitted in accordance with the DCI message and thereference signal association flag.

FIG. 20A illustrates a flow diagram of example operations 2000 occurringin a UE communicating (e.g., transmitting or receiving) a referencesignal based on a reference signal association flag received for an DCImessage triggering the reference signal transmission and scheduling a ULdata transmission. Operations 2000 may be indicative of operationsoccurring in a UE as the UE communicates (e.g., transmits or receives) areference signal (e.g., a SRS or CSI-RS) based on a reference signalassociation flag received in a DCI message scheduling a UL datatransmission. The reference signal association flag may be received froman access node serving the UE, for example. The reference signalassociation flag may be received in a DCI message, a MAC CE, or aconfiguration RRC signaling.

Operations 2000 begin with the UE receiving a DCI message scheduling aUL data transmission (block 2005). The DCI message including a referencesignal trigger, and in some embodiments, a reference signal associationflag. As discussed previously, the reference signal association flag mayindicate (based on the indicated value) that the UE should communicate(transmit or receive) a reference signal (e.g., transmit the SRS,receive the CSI-RS, etc.) in accordance with parameters signaled to theUE in a DCI message (which may be the same DCI message or a differentDCI message) for another purpose. As an example, based on the referencesignal association flag, the UE may utilize the PUSCH parameterssignaled in a DCI message or CSI request parameters signaled in a DCImessage. In an embodiment, in the situation where the UE uses the CSIrequest parameters to transmit the reference signal, the DCI messagealso includes a CSI request. As another example, based on the referencesignal association flag, the UE may utilize parameters based onpre-configuration signaled in RRC signaling configuring the referencesignal.

The UE performs a check to determine if the reference signal associationflag is set to a specified value (block 2007). If the reference signalassociation flag is set to the specified value, the UE communicates(transmits or receives) the reference signal (e.g., the SRS, the CSI-RS,etc.) in accordance with parameters signaled to the UE in a DCI messagefor another purpose such as for the PUSCH transmission (block 2009). Ifthe reference signal association flag is not set to the specified value,the UE communicates (transmits or receives) the reference signal inaccordance with parameters signaled to the UE in a RRC message (block2011).

FIG. 20B illustrates a flow diagram of example operations 2050 occurringin an access node receiving (or transmitting) a reference signal basedon a reference signal association flag transmitted in a DCI messagescheduling a UL transmission. Operations 2050 may be indicative ofoperations occurring in an access node as the access node receives (ortransmits) a reference signal (e.g., a SRS or CSI-RS) based on areference signal association flag transmitted in a DCI message. Thereference signal association flag may be transmitted by the access nodeserving the UE, for example. The reference signal association flag maybe transmitted in a DCI message, MAC CE, or RRC signaling.

Operations 2050 begin with the access node transmitting a DCI message(block 2055). The DCI message may be transmitted to a UE, multiple UEs,or a group of UEs to schedule a UL transmission. The DCI message mayinclude a reference signal association flag. As discussed previously,the reference signal association flag may indicate (based on theindicated value) that the UE should transmit (or receive) a referencesignal (e.g., the SRS, the CSI, etc.) in accordance with parameterssignaled to the UE in a DCI message. As an example, based on thereference signal association flag, the UE may utilize the PUSCHparameters signaled in a DCI message or CSI request parameters signaledin a DCI message. In an embodiment, in the situation where the UE usesthe CSI request parameters to transmit the reference signal, the DCImessage also includes a CSI request. As another example, based on thereference signal association flag, the UE may utilize parameterssignaled based on pre-configuration in RRC signaling configuring thereference signal. The access node communicates (transmits or receives)the reference signal (block 2057). The reference signal beingtransmitted or received in accordance with the DCI message and thereference signal association flag.

In some embodiments, the PDSCH transmission is one of multiple PDSCHtransmissions following a DCI, and the DCI includes a reference signalassociation flag. In an embodiment, the PDSCH is a semi-persistentscheduled (SPS) PDSCH activated by the DCI, and the SRS is asemi-persistent (SP) SRS activated by the DCI, and the DCI includes aCyclic redundancy check (CRC) scrambled by a Configured Scheduling (CS)Radio Network Temporary Identifier (RNTI) (CS-RNTI). For SPS PDSCH, sometransmission parameters are configured by RRC configuration signaling,but some other transmission parameters, e.g., FDRA and modulation order,are provided by a DCI with a CRC scrambled by a CS-RNTI. After receivingthe DCI, the SPS PDSCH will be periodically received by the UE accordingto a periodicity configured by RRC configuration signaling, i.e., theSPS PDSCH is activated by the DCI, until the UE receives another DCIwith a CRC scrambled by a CS-RNTI to deactivate or modify the SPS PDSCH.In some sense, the SPS PDSCH transmissions reuse the same DCI (theactivation DCI) for multiple periodic PDSCH. The SPS PDSCH is useful forperiodic traffic loads with reduced scheduling latency and DCI overhead,such as in URLLC and XR.

The use of a DCI as opposed to MAC CE for activation has the benefit ofreduced latency. In an embodiment, the DCI that activates the SPS PDSCHalso activates the SP-SRS for interference probing. The SP-SRStransmission parameters, e.g., the FDRA, PRB allocation, spatial-domainparameters, periodicity, etc., are the same as the SPS PDSCH'sparameters if the reference signal association is set to a specificvalue. Therefore, one or more slots before each of the PDSCHtransmissions, a SRS is transmitted to probe the interference, and theaccess node then adjusts the PDSCH precoding for the PDSCH transmission,and this repeats for multiple SRS/PDSCH transmissions. In an embodiment,the SRS periodicity is a multiple of the PDSCH periodicity, that is, oneSRS probing outcome may be used for several PDSCH transmissions. In anembodiment, semi-persistent CSI-RS and optionally CSI-IM may also beactivated by the same DCI and sent before each SRS transmission so thatthe SRS may adjust its precoding based on the CSI-RS/CSI-IM. Theseembodiments have the advantages that multiple SRS probing operations andmultiple PDSCH transmissions can be supported with a single DCI andhence, has very low control overhead. Furthermore, the PDSCHtransmissions may progressively improve as the procedure effectivelybecomes iterative BIT, which is suitable for, e.g., XR with veryfrequent and periodic traffic arrivals, fixed wireless access (FWA),etc. With the reference signal association flag, the reference signaltransmissions (e.g., the SRS transmissions) may be based on either thesame parameters as the PDSCH transmissions or the pre-configured SRSparameters.

In some embodiments, one DCI may schedule multiple PDSCH transmissionsover multiple slots, i.e., multi-slot scheduling or PDSCH repetition,and PDSCH precoding adjustment can be performed for the PDSCHtransmissions after the A-SRS transmission triggered by the DCI. In yetsome other embodiments, periodic, semi-persistent PDSCH, SRS, or CSI-RSare specified by higher-layer signaling such as RRC configurationsignaling or MAC CE without using any DCI, and the SRS still reuses thePDSCH parameters for its transmission, e.g., the frequency-domain orspatial-domain parameters if the reference signal association flag isset to a specific value, and uses pre-configured SRS parameters for itstransmission if the reference signal association flag is not set to thespecific value. If the PDSCH parameters are configured to change overdifferent TTIs, the SRS transmission immediately before a PDSCHtransmission also adopts the same parameters as the PDSCH, for example.

FIG. 21 illustrates an example communication system 2100. In general,the system 2100 enables multiple wireless or wired users to transmit andreceive data and other content. The system 2100 may implement one ormore channel access methods, such as code division multiple access(CDMA), time division multiple access (TDMA), frequency divisionmultiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA(SC-FDMA), or non-orthogonal multiple access (NOMA).

In this example, the communication system 2100 includes electronicdevices (ED) 2110 a-2110 c, radio access networks (RANs) 2120 a-2120 b,a core network 2130, a public switched telephone network (PSTN) 2140,the Internet 2150, and other networks 2160. While certain numbers ofthese components or elements are shown in FIG. 21 , any number of thesecomponents or elements may be included in the system 2100.

The EDs 2110 a-2110 c are configured to operate or communicate in thesystem 2100. For example, the EDs 2110 a-2110 c are configured totransmit or receive via wireless or wired communication channels. EachED 2110 a-2110 c represents any suitable end user device and may includesuch devices (or may be referred to) as a user equipment or device (UE),wireless transmit or receive unit (WTRU), mobile station, fixed ormobile subscriber unit, cellular telephone, personal digital assistant(PDA), smartphone, laptop, computer, touchpad, wireless sensor, orconsumer electronics device.

The RANs 2120 a-2120 b here include base stations 2170 a-2170 b,respectively. Each base station 2170 a-2170 b is configured towirelessly interface with one or more of the EDs 2110 a-2110 c to enableaccess to the core network 2130, the PSTN 2140, the Internet 2150, orthe other networks 2160. For example, the base stations 2170 a-2170 bmay include (or be) one or more of several well-known devices, such as abase transceiver station (BTS), a Node-B (NodeB), an evolved NodeB(eNodeB), a Next Generation (NG) NodeB (gNB), a Home NodeB, a HomeeNodeB, a site controller, an access point (AP), or a wireless router.The EDs 2110 a-2110 c are configured to interface and communicate withthe Internet 2150 and may access the core network 2130, the PSTN 2140,or the other networks 2160.

In the embodiment shown in FIG. 21 , the base station 2170 a forms partof the RAN 2120 a, which may include other base stations, elements, ordevices. Also, the base station 2170 b forms part of the RAN 2120 b,which may include other base stations, elements, or devices. Each basestation 2170 a-2170 b operates to transmit or receive wireless signalswithin a particular geographic region or area, sometimes referred to asa “cell.” In some embodiments, multiple-input multiple-output (MIMO)technology may be employed having multiple transceivers for each cell.

The base stations 2170 a-2170 b communicate with one or more of the EDs2110 a-2110 c over one or more air interfaces 2190 using wirelesscommunication links. The air interfaces 2190 may utilize any suitableradio access technology.

It is contemplated that the system 2100 may use multiple channel accessfunctionality, including such schemes as described above. In particularembodiments, the base stations and EDs implement 5G New Radio (NR), LTE,LTE-A, or LTE-B. Of course, other multiple access schemes and wirelessprotocols may be utilized.

The RANs 2120 a-2120 b are in communication with the core network 2130to provide the EDs 2110 a-2110 c with voice, data, application, Voiceover Internet Protocol (VoIP), or other services. Understandably, theRANs 2120 a-2120 b or the core network 2130 may be in direct or indirectcommunication with one or more other RANs (not shown). The core network2130 may also serve as a gateway access for other networks (such as thePSTN 2140, the Internet 2150, and the other networks 2160). In addition,some or all of the EDs 2110 a-2110C may include functionality forcommunicating with different wireless networks over different wirelesslinks using different wireless technologies or protocols. Instead ofwireless communication (or in addition thereto), the EDs may communicatevia wired communication channels to a service provider or switch (notshown), and to the Internet 2150.

Although FIG. 21 illustrates one example of a communication system,various changes may be made to FIG. 21 . For example, the communicationsystem 2100 could include any number of EDs, base stations, networks, orother components in any suitable configuration.

FIGS. 22A and 22B illustrate example devices that may implement themethods and teachings according to this disclosure. In particular, FIG.22A illustrates an example ED 2210, and FIG. 22B illustrates an examplebase station 2270. These components could be used in the system 2100 orin any other suitable system.

As shown in FIG. 22A, the ED 2210 includes at least one processing unit2200. The processing unit 2200 implements various processing operationsof the ED 2210. For example, the processing unit 2200 could performsignal coding, data processing, power control, input/output processing,or any other functionality enabling the ED 2210 to operate in the system2100. The processing unit 2200 also supports the methods and teachingsdescribed in more detail above. Each processing unit 2200 includes anysuitable processing or computing device configured to perform one ormore operations. Each processing unit 2200 could, for example, include amicroprocessor, microcontroller, digital signal processor, fieldprogrammable gate array, or application specific integrated circuit.

The ED 2210 also includes at least one transceiver 2202. The transceiver2202 is configured to modulate data or other content for transmission byat least one antenna or NIC (Network Interface Controller) 2204. Thetransceiver 2202 is also configured to demodulate data or other contentreceived by the at least one antenna 2204. Each transceiver 2202includes any suitable structure for generating signals for wireless orwired transmission or processing signals received wirelessly or by wire.Each antenna 2204 includes any suitable structure for transmitting orreceiving wireless or wired signals. One or multiple transceivers 2202could be used in the ED 2210, and one or multiple antennas 2204 could beused in the ED 2210. Although shown as a single functional unit, atransceiver 2202 could also be implemented using at least onetransmitter and at least one separate receiver.

The ED 2210 further includes one or more input/output devices 2206 orinterfaces (such as a wired interface to the Internet 2150). Theinput/output devices 2206 facilitate interaction with a user or otherdevices (network communications) in the network. Each input/outputdevice 2206 includes any suitable structure for providing information toor receiving information from a user, such as a speaker, microphone,keypad, keyboard, display, or touch screen, including network interfacecommunications.

In addition, the ED 2210 includes at least one memory 2208. The memory2208 stores instructions and data used, generated, or collected by theED 2210. For example, the memory 2208 could store software or firmwareinstructions executed by the processing unit(s) 2200 and data used toreduce or eliminate interference in incoming signals. Each memory 2208includes any suitable volatile or non-volatile storage and retrievaldevice(s). Any suitable type of memory may be used, such as randomaccess memory (RAM), read only memory (ROM), hard disk, optical disc,subscriber identity module (SIM) card, memory stick, secure digital (SD)memory card, and the like.

As shown in FIG. 22B, the base station 2270 includes at least oneprocessing unit 2250, at least one transceiver 2252, which includesfunctionality for a transmitter and a receiver, one or more antennas2256, at least one memory 2258, and one or more input/output devices orinterfaces 2266. A scheduler, which would be understood by one skilledin the art, is coupled to the processing unit 2250. The scheduler couldbe included within or operated separately from the base station 2270.The processing unit 2250 implements various processing operations of thebase station 2270, such as signal coding, data processing, powercontrol, input/output processing, or any other functionality. Theprocessing unit 2250 can also support the methods and teachingsdescribed in more detail above. Each processing unit 2250 includes anysuitable processing or computing device configured to perform one ormore operations. Each processing unit 2250 could, for example, include amicroprocessor, microcontroller, digital signal processor, fieldprogrammable gate array, or application specific integrated circuit.

Each transceiver 2252 includes any suitable structure for generatingsignals for wireless or wired transmission to one or more EDs or otherdevices. Each transceiver 2252 further includes any suitable structurefor processing signals received wirelessly or by wire from one or moreEDs or other devices. Although shown combined as a transceiver 2252, atransmitter and a receiver could be separate components. Each antenna2256 includes any suitable structure for transmitting or receivingwireless or wired signals. While a common antenna 2256 is shown here asbeing coupled to the transceiver 2252, one or more antennas 2256 couldbe coupled to the transceiver(s) 2252, allowing separate antennas 2256to be coupled to the transmitter and the receiver if equipped asseparate components. Each memory 2258 includes any suitable volatile ornon-volatile storage and retrieval device(s). Each input/output device2266 facilitates interaction with a user or other devices (networkcommunications) in the network. Each input/output device 2266 includesany suitable structure for providing information to orreceiving/providing information from a user, including network interfacecommunications.

FIG. 23 is a block diagram of a computing system 2300 that may be usedfor implementing the devices and methods disclosed herein. For example,the computing system can be any entity of UE, access network (AN),mobility management (MM), session management (SM), user plane gateway(UPGW), or access stratum (AS). Specific devices may utilize all of thecomponents shown or only a subset of the components, and levels ofintegration may vary from device to device. Furthermore, a device maycontain multiple instances of a component, such as multiple processingunits, processors, memories, transmitters, receivers, etc. The computingsystem 2300 includes a processing unit 2302. The processing unitincludes a central processing unit (CPU) 2314, memory 2308, and mayfurther include a mass storage device 2304, a video adapter 2310, and anI/O interface 2312 connected to a bus 2320.

The bus 2320 may be one or more of any type of several bus architecturesincluding a memory bus or memory controller, a peripheral bus, or avideo bus. The CPU 2314 may comprise any type of electronic dataprocessor. The memory 2308 may comprise any type of non-transitorysystem memory such as static random access memory (SRAM), dynamic randomaccess memory (DRAM), synchronous DRAM (SDRAM), read-only memory (ROM),or a combination thereof. In an embodiment, the memory 2308 may includeROM for use at boot-up, and DRAM for program and data storage for usewhile executing programs.

The mass storage 2304 may comprise any type of non-transitory storagedevice configured to store data, programs, and other information and tomake the data, programs, and other information accessible via the bus2320. The mass storage 2304 may comprise, for example, one or more of asolid state drive, hard disk drive, a magnetic disk drive, or an opticaldisk drive.

The video adapter 2310 and the I/O interface 2312 provide interfaces tocouple external input and output devices to the processing unit 2302. Asillustrated, examples of input and output devices include a display 2318coupled to the video adapter 2310 and a mouse, keyboard, or printer 2316coupled to the I/O interface 2312. Other devices may be coupled to theprocessing unit 2302, and additional or fewer interface cards may beutilized. For example, a serial interface such as Universal Serial Bus(USB) (not shown) may be used to provide an interface for an externaldevice.

The processing unit 2302 also includes one or more network interfaces2306, which may comprise wired links, such as an Ethernet cable, orwireless links to access nodes or different networks. The networkinterfaces 2306 allow the processing unit 2302 to communicate withremote units via the networks. For example, the network interfaces 2306may provide wireless communication via one or more transmitters/transmitantennas and one or more receivers/receive antennas. In an embodiment,the processing unit 2302 is coupled to a local-area network 2322 or awide-area network for data processing and communications with remotedevices, such as other processing units, the Internet, or remote storagefacilities.

It should be appreciated that one or more steps of the embodimentmethods provided herein may be performed by corresponding units ormodules. For example, a signal may be transmitted by a transmitting unitor a transmitting module. A signal may be received by a receiving unitor a receiving module. A signal may be processed by a processing unit ora processing module. The respective units or modules may be hardware,software, or a combination thereof. For instance, one or more of theunits or modules may be an integrated circuit, such as fieldprogrammable gate arrays (FPGAs) or application-specific integratedcircuits (ASICs).

Although the present disclosure and its advantages have been describedin detail, it should be understood that various changes, substitutionsand alterations can be made herein without departing from the scope ofthe disclosure as defined by the appended claims.

What is claimed is:
 1. A method implemented by an access node, themethod comprising: transmitting, by the access node to a user equipment(UE), a control information message comprising a downlink controlinformation (DCI) message and an association indicator indicating anassociation between a reference signal and a channel between the accessnode and the UE; and communicating, by the access node with the UE, thereference signal in accordance with at least one channel parameterassociated with the channel between the access node and the UE.
 2. Themethod of claim 1, the channel being a Physical Data Shared Channel(PDSCH) scheduled by the DCI or configured as a semi-persistentscheduled (SPS) PDSCH.
 3. The method of claim 1, the channel being aphysical uplink shared channel (PUSCH) scheduled by the DCI orconfigured as a grant.
 4. The method of claim 1, the channel being aphysical downlink shared channel (PDSCH), and the at least one channelparameter comprising at least one PDSCH parameter comprising a frequencydomain resource assignment (FDRA) or an antenna port assignmentcomprising at least one of an antenna port number, an antenna port, anda number of layers.
 5. The method of claim 1, the association indicatorindicating the association between the reference signal and the channelconveying a channel state information (CSI) request.
 6. The method ofclaim 1, the channel being a physical uplink shared channel (PUSCH), theat least one channel parameter comprising at least one PUSCH parametercomprising at least one of a carrier indicator, an uplink (UL)indicator, a supplementary UL (SUL) indicator, a bandwidth part (BWP)indicator, a FDRA, a time domain resource assignment (TDRA), a frequencyhopping flag, a transmit power control (TPC) command, a SRS resourceindicator, precoding information and number of layers information(TPMI), antenna ports, a SRS request, or a CSI request.
 7. The method ofclaim 1, the association indicator indicating a non-association betweenthe reference signal and the channel, and the method further comprisingcommunicating, by the access node with the UE, the reference signal inaccordance with parameters configured for the reference signal.
 8. Themethod of claim 1, the communicating the reference signal in accordancewith the at least one channel parameter comprising at least one of:receiving, from the UE, the reference signal in accordance with the atleast one channel parameter associated with the channel between theaccess node and the UE, or transmitting, to the UE, the reference signalin accordance with the at least one channel parameter associated withthe channel between the access node and the UE.
 9. The method of claim1, the reference signal comprising a sounding reference signal (SRS), achannel state information reference signal (CSI-RS), or a CSI forinterference measurement (CSI-IM).
 10. A method implemented by a userequipment (UE), the method comprising: receiving, by the UE from anaccess node, a control information message comprising a downlink controlinformation (DCI) message and an association indicator indicating anassociation between a reference signal and a channel between the accessnode and the UE, the channel being a physical downlink shared channel(PDSCH) scheduled by the DCI and configured as a semi-persistentscheduled (SPS) PDSCH, a physical uplink shared channel (PUSCH)scheduled by the DCI, or the channel being configured as a grant; andcommunicating, by the UE with the access node, the reference signal inaccordance with at least one channel parameter associated with thechannel between the access node and the UE.
 11. The method of claim 10,the channel being the PDSCH, the at least one channel parametercomprising at least one PDSCH parameter comprising a frequency domainresource assignment (FDRA) or an antenna port assignment comprising atleast one of an antenna port number, an antenna port, and a number oflayers.
 12. The method of claim 10, the channel being the PUSCH, the atleast one channel parameter comprising at least one PUSCH parametercomprising at least one of a carrier indicator, an uplink (UL)indicator, a supplementary UL (SUL) indicator, a bandwidth part (BWP)indicator, a time domain resource assignment (TDRA), a frequency hoppingflag, a transmit power control (TPC) command, a SRS resource indicator,precoding information and number of layers information (TPMI), antennaports, a SRS request, or a CSI request.
 13. The method of claim 10, theassociation indicator indicating a non-association between the referencesignal and the channel, and the method further comprising communicating,by the access node with the UE, the reference signal in accordance withparameters configured for the reference signal.
 14. The method of claim10, the communicating the reference signal in accordance with the atleast one channel parameter comprising at least one of: receiving, fromthe access node, the reference signal in accordance with the at leastone channel parameter associated with the channel between the accessnode and the UE, or transmitting, to the access node, the referencesignal in accordance with the at least one channel parameter associatedwith the channel between the access node and the UE.
 15. The method ofclaim 10, the channel being a PUSCH and the control information messagefurther comprising at least one of a SRS TDRA or a SRS TPC command. 16.The method of claim 10, the reference signal comprising a soundingreference signal (SRS), a channel state information reference signal(CSI-RS), or a CSI for interference measurement (CSI-IM).
 17. An accessnode, comprising: one or more processors; and a non-transitory memorystorage storing instructions that, when executed by the one or moreprocessors, cause the access node to perform operations including:transmitting, to a user equipment (UE), a control information messagecomprising a downlink control information (DCI) message and anassociation indicator indicating an association between a referencesignal and a channel between the access node and the UE; andcommunicating, with the UE, the reference signal in accordance with atleast one channel parameter associated with the channel between theaccess node and the UE.
 18. A user equipment (UE), comprising: one ormore processors; and a non-transitory memory storage storinginstructions that, when executed by the one or more processors, causethe UE to perform operations including: receiving, from an access node,a control information message comprising a downlink control information(DCI) message and an association indicator indicating an associationbetween a reference signal and a channel between the access node and theUE; and communicating, with the access node, the reference signal inaccordance with at least one channel parameter associated with thechannel between the access node and the UE.